Skip to main content

Full text of "Radio Electronics (May 1991)"

See other formats


ECHNOLOGY - VIDEO - STEREO - COMPUTERS - SERVI 



UILD THIS DRAM TESTER „ 
OR LESS THAN £60! ' 



KV 1 

volt 



eter mining whether 
our dynaTnte^ 
tAM chips are 
jnctioning properly 
nd at the rated. 
peed. 

'UILD THE 
HONE-CO 

Jse your telephones as a 
lome intercom/system. 

UILD A PULSE ^L\ 

ENERATOR 

Jur handheld Pulse-IVfate Is 
i handy troubleshooting -tool, 

WITCHING 
EGULATORS 

i he heart of switching,'' 
>ower supplies. /' / 

C-BASEDTEST ff — 
QUIPMENT 

:xperimenting with the 
osic concepts. 



^ G 






■OH^Ve ^ 







— \ 




$2.95 U.S. 
S3.75 CAN 



GERNSBACK 



xxx***xx CAR-RT SORT xx CRQ3 
75D456HRR5165M093 D5 05 

SEP 91 
RE 




FLUKE AND PHILIPS - THE GLOBAL ALLIANCE IN TEST & MEASUREMENT 



FLUKE 73 


FLUKE 75 


m- 


tlt9" 


MfcglDUttlfeptft 


»Jliio»1>olal|jBtiU( 


Vote, ohms TO 
flUMdl rtooe lest 

axuncj 

ax»+ row 

baise* i We 


rM loorh heedl 
diode lei 

Oi* basic * 

accuracy 

AuoKrie conlJftjity 


3- year warranty 


AutcrmgcAange hold 




2M0+ how 




bartwviirt 




SyearwaiiaiTly 


■Sugo«twU.S Istorra 







FLUKE 77 




PHILIPS 



More than two million users agree: the 

Fluke 70 Series handheld digital multimeters 
are amply the best. 

These originals have become classics. And 
the reasons are simple. 

They are accurate and easy to use. Features 
made popular by the 70 Series-like fast 
autoranging, continuity beeper, and quick 
diode test-are now standards in the industry. 

Other 70 Series features stand alone. Touch 
Hold®, for example, locks the reading on 
the display and signals you with a beep. So 



you can keep your eyes on the circuit and 
probes. 

The 70 Series are built without compromise. 
All current ranges are fully fused. The 
resistance function is overload protected to 
500V. No detail has been overlooked in 
making these rugged and reliable meters 
the first choice of two million professionals. 

Made in the USA using state-of-the-art man- 
ufacturing methods, every Fluke 70 Series 
multimeter is backed by a 3-year warranty. 
Another first in the industry. 



Choosing the best handheld multimeter is 
very simple. Pick up the Fluke 70 Series at 
your Fluke distributor today. Or call 
1-800-44-FLUKE, exl33, for a free 

brochure. 

John Fluke Mlg. Co.. Inc. P.O. Box 9090, Everett. WA 98206- J.S.: 
(206) 356-5400. Canada: (116) 890-7600. Other countries: [206) 
356-5500 © 1990 John Fluke Mfg. Co.. Inc. All rights reserved 
Ad.r»,O7O1-F70 

FROM THE WORLD LEADER 
IN DIGITAL MULTIMETERS. 



FLUK 



CIRCLE 121 ON FHEE INFORMATION CARD 




ay 1991 






Vol. 62 No. 5 




33 DRAM TESTER 

Build an under-$60 DRAM unit that performs dynamic-RAM function, 
speed, and margin tests. 
Fred Hufft 

41 PULSE-MATE 

Our Inexpensive single-shot and continuous-pulse generator offers 
positive and negative pulses. 
David Plant 

44 USE YOUR TELEPHONES AS A HOME INTERCOM 
SYSTEM 

It's easy to do with our controller board and alert modules! 
Frank Polimene 

56 EXPERIMENTING WITH PC-BASED TEST EQUIPMENT 

Build your own low-cost PC- based test equipment. 
James J. Barbarello 




49 INSIDE SWITCHING POWER SUPPLIES 

Learn some applications of, and basic troubleshooting techniques 
for, two switching regulator IC families. 
Harry L. Trietely 

61 PERSONAL COMMUNICATION NETWORK 

Can PCN microcell technology make affordable mobile 
communications a reality? 
Roger P. Newell 



I 



6 VIDEO NEWS 

What's new in this fast- 
changing field. 
David Lachenbruch 

65 HARDWARE HACKER 

More on toner-cartridge 

reloading and Santa Claus 

machines! 

Don Lancaster 

72 AUDIO UPDATE 

Audio Amplifiers: Do they 
sound different? 
Larry Klein 



75 DRAWING BOARD 

A simple, inexpensive logic 

probe. 

Robert Grossblatt 

77 COMPUTER 
CONNECTIONS 

Video standards. 
Jeff Holtzman 



PULSE-MATE 





"'""*"" — *"— 


nn 


Wj i ~^B 







PAGE 41 




TELEPHONES 
AS A HOME 
INTERCOM 

SYSTEM 





^ ^srpa==3 =^r=n=; 






invM^ 


'spS=5=|pg| 


I fcmri \\* + 


§fe";'=H SSjSHgs: 


[S***~ 


--.*■■■. Vjmj ILiiJJiSii 




PAGE 44 


V' N I , 


^ikpB 



96 Advertising and Sales 
Offices 

96 Advertising Index 

12 Ask RE 

14 Letters 

84 Market Center 

28 New Lit 

22 New Products 

4 What's News 

50A RE-Shopper* 



i 



"Included in selected issues only. 




to 
o 

z 
o 

DC 

o 
w 



< 




If you've ever had to expand your 
PC's RAM capacity, troubles hoot a 
memory problem, or upgrade the cy- 
cle speed of a memory band, you've 
had the need for a dynamic RAM 
(DRAM) tester like the one featured 
on page 33. Our DRAM tester pro- 
vides an easy method of function 
testing and measuring the speed 
(access time) of DRAM IC's, You 
could spend anything from $150 to 
$1 000 to buy a DRAM tester. Or you 
could build ourmultifunction unit — 
which can function test, accurately 
test speed, and automatically cycle 
the tests under high-, low-, or nor- 
mal-voltage margins — for less than 
$60! 



COMING NEXT MONTH 



THE JUNE ISSUE 

GOES ON SALE 

MAY 7. 



BUILD A 50-MHZ LOGIC ANALYZER 

Portable unit with its own LCD, can also be interfaced to your PC. 

BUILD AN ELECTRONIC COMPASS 

A Hall-effect sensor shows you the way. 

VOLTAGE-TO-FREQUENCY CONVERTERS 
How to use them in your designs. 

PC BASED TEST EQUIPMENT 

More experiments teach the basics of PC-based test equipment. 



A* a service to readers. RADIO-ELECTRONICS publishes available plans or information relating to newsworthy products, 
techniques and scientific and technological developments. Because of possible variances in the quality and condition of 
materials and workmanship used by readers. RADIO -ELECTRONICS disclaims any responsibility for the safe and proper 
functioning of reader-built projects based upon or from plans or information published in this magazine. 

Since some of the equipment and circuitry described in HADIO-ELECTRQNICS may relate to or be covered by U.S. patents, 
RADIO-ELECTRONICS disclaims any liability for th a infringement of such patents by the making, using, or selling of any such 
equipment or circuitry, and suggests that anyone interested in such projects consult a patent attorney. 

RADIO-ELECTRONICS. (ISSN 0033-7862) May 1991. Published monthly by Gemsback Publications, Inc., 500- B Si-County 
Boulevard, Farmingdale, NY 1 1 735 Second-Class Postage paid atFarmingdale, NY and additional mailing offices. Second-Class 
mail registration No. 9242. authorized at Toronto. Canada. One-year subscription rate USA. and possessions $17.97. Canada 
S25.65 (includes G.S.T. Canadian Goods and Services Tax Registration No. R1351662SO), all other countries $26.97 All 
subscription orders payable in U.S.A. funds only, via international postal money order or check drawn on a USA bank. Single 
copies $2-95- & 1991 by Gemsback Publications. Inc. All rights reserved. Printed in U.SA 

POSTMASTER: Please send address changes to fiADIO-ELECTRONICS, Subscription DepL, Box 55115, Boulder, CO 
80321-5115. 

A stamped self-addressed envelope must accompany all submitted manuscripts and/or artwork or photographs if their return is 
desired should they be rejected. We disclaim any responsibility for the less or damage of manuscripts end/or artwork or 
photographs while in our possession or otherwise. 



firf?<T'fHr 



Hugo Gemsback ,1884-1967) founder 

Larry Stockier, EKF, GET. 
editor iivchicf and publisher 

EDITORIAL DEPARTMENT 
Brian C. Fcnton, editor 
Marc Spiwtik, associate editor 
Kim Dunleavy* 

assistant technical editor 
Ten Scaduto, assistant editor 
Jeffrey K, Holtzman 

computer editor 
Robert GrossblatL, circuits editor 
Larry Klein, audio editor 
David Lachenbruch 

contributing editor 
Don Lancaster 

contributing editor 
Richard D. Filch 

contributing editor 
Kathy Terenzi, editorial assistant 

ART DEPARTMENT 
Andre Duzant. art director 
Injae Lee, illustrator 
Russell C.TrueJson, illustrator 

PRODUCTION DEPARTMENT 
Ruby M. Yee. production director 
Janice Bon, 

editorial production 
Karen S. Brown 

advertising production 
MarceJLa Amoroso 

production assistant 

CIRCULATION DEPARTMENT 
Jacqueline P. Cheese bo ro 

circulation director 
Wendy Alanko 

circulation analyst 
Theresa Lombardo 

circulation assistant 
Michele Tom Ha, reprint bookstore 

Typography by Mates Graphics 
Cover photo by Diversified Photo 
Services 

Radio Electronics is indexed in 
Applied Science 1 Technology Index 
and Readers Guide to Periodical Liter' 
flftfnt. 

Microfilm & Microfiche editions are 
available. Contact circulation depart- 
ment for details. 

Advertising Sales Offices listed 

on page 98. 

Radio- Electronics Executive and 

Administrative Offices 

t -51 6 293-3000, 
Subscriber Customer Service: 

1*800 288-0852. 
Order Entry for New Subscribers: 

1-80O- 999- 7 139. 




A Shocking Offer! 



Now for the first time in CIE's 56 year history you do 
not have to be enrolled at CI E to receive our introduc- 
tory Electronic and Electricity Lesson Modules. 
Available for a limited time to non-students for the 
shockingly low price of only $149.50 

With CIE's patented AUTO-PROGRAMMED 
method of learning you'll quickly learn and then 
master the basics of electronics and electricity and 
then move on to... DC/AC circuit 
theories, fundamentals of bi-polar 
junction transistors (BJT), field 
effect transistors (FET), 
wiring, diagram and sche- 
matic readings, component 
identification, soldering 
techniques... and much, 
much, more. 

Your commitment to CIE 
ends with your payment, but 
CIE's commitment to your 
success just begins when you 
receive your 



39 lessons, exams, binders and equipment. This 
special introductory price Includes all the benefits and 
assistance CIE normally extends to its students and 
graduates. You'll be entitled to unlimited access to 
CIE's faculty and staff to assist you in your studies via 
a toll free 800 number six days a week, 24-hour 
turnaround on grading your submitted exams, CIE 
Bookstore privileges, a patented learning method, 

reference library, a student, faculty 
and alumni electronic 
bulletin board and a free 
issue of CIE's school 
newspaper The Electron. 
All this knowledge and 
support will put you on the 
road to understanding 
digital electronics, 
microprocessing principles, 
computer systems, telecom- 
munications, and 
much, much, 




- Free Issue of The Electron 

• Build your personal burglar alarm 

• Instructors available 6 days a week 

• 20 lesson books containing 39 
theory and hands-on training 
lessons and exams. 



■ Bookstore Privileges 

• Patented Learning Method 

• Electronic Bulletin Board 

• 24-Hour Grading 



O Yes, send me CIE's 39 Introductory Electronic 
and Electricity Lessons and Equipment. 

Name: 



Address: 

City: 

State: _ 
Age: 



_Apt. #: 



_Zip: 



Phone 



MM 



BOOKSTORE 

I77IV Kusl 1 7th Sln-rl 
Qt'vi'huuLOtiti.Min 
(216) J81-9400 



Total Merchandise: , , 

Ohio Residents add 7% Sales Tax. 
California Residents add 6-1/2% Sales Tax: 
Total this order: 



$149.50 



Method of Payment: Amount Enclosed . . . $ 

~i Personal Check or Money Order 
1 Master Card □ Visa 

□□□□□□□□□□□□□□DO 
Card Expiration Date: 



Signature . 



CHARGE BY PHONE! 



9 AM to 4:30 PM Eastern Time; from Ohio 1-800-523-9109 
from all other states 1-800-321-2155 



s 

5 



WHAT'S NEWS 



A review of the latest happenings in electronics. 



All-digital HDTV development 

Major changes have occurred in 
the US development of HDTV over 
the past few years. Where NTSC- 
compatible systems were the early 
favorites, the FCC has indicated that 
it will select a simulcast 6-MHz HDTV 
broadcast standard in 1993 — and it is 
unlikely that the FCC will even con- 
sider any analog systems. 

After 18 months of cooperative 
effort, Zenith Electronics Corpora- 
tion CGIenview. ID, AT&T Bell Labora- 
tories, and AT&T Microelectronics 
unveiled an all-digital high-definition 
system that is said to solve many of 
the problems associated with simul- 
casting. Zenith handled system defi- 
nition and transmission technology, 
AT&T Bell Labs designed and imple- 
mented a new video-compression 
system, and AT&T Microelectronics 
supplied the necessary semiconduc- 
tor technology. 

Interference now renders unusable 
many standard 6-MHz channels in 
the VHF and UHF broadcast spec- 
trum, including those that are tar- 
geted to carry HDTV simulcasts. 
Building upon key elements of 
Zenith's previously proposed, par- 
tially digital "Spectrum Compatible" 
HDTV, the Zenith/AT&T system uses 
an advanced digital filtering system 
that prevents high-powered NTSC 
signals from interfering with HDTV 
signals, allowing use of those cur- 
rently taboo channels. The system, 
which uses a unique digital filterat the 
HDTV transmitter and a complemen- 
tary filter in the HDTV receiver, is said 
to offer interference- and noise-free 
signals. 

AT&T's research in digital video 
compression, channel equalization 
(ghost canceling), and advanced 
high-speed processors rounded out 
the system. A critical element is a 
video-compression algorithm that is 
used to squeeze the enormous 
amount of HDTV data into a 6-MHz 
channel without loss of resolution. 
The compression technique involves 
motion compensation, analysis of 
each frame to prepare it for transmis- 
sion, and modification of the signal to 



compensate for the properties of 
human vision and the idiosyncrasies 
of the 6-MHz channels. The HDTV 
system required high-speed digital 
signal processors (DSP's), de- 
veloped by AT&T Microelectronics, to 
perform the filtering, data encoding, 
and formatting functions. 

The result of all that cooperation is 
an HDTV system that transmits 1 575 
horizontal picture lines 30 times a 
second Ccompaied to 1125 or 1050 
lines from competing systems). It 
uses progressive scan with square 
pixels, making it easier to interface 
with computer workstations and to 
eliminate the jagged edges and other 
artifacts. Zenith says the system pro- 
vides "movie-theater-quality pictures 
and four-channel compact-disc quali- 
ty digital audio." 

We'll learn if their system has what 
it takes when testing of the five sys- 
tems remaining in the HDTV race 
(from an original field of more than 
twenty) begins this fall by the Ad- 
vanced Television Testing Center, Ca- 
ble Television Laboratories Inc.. and 
the Canadian Communications Re- 
search Center. After testing is com- 
pleted, the FCC's Advisory Commit- 
tee on Advanced Television Services 
is expected to recommend one as the 
standard in 1992. The FCC is ex- 
pected to consider their recommen- 




We 
Want 

LISTENING 

Fbi A Lifetime __ 



THE EIA'S HEARING-SAFETY CAM- 
PAIGN, launched in January at the Winter 
Consumer Electronics Show, aims to edu- 
cate consumers about the dangers of too- 
high decibel levels. 



dation and select a standard in the 
second quarter of 1993. 

National hearing-safety 
campaign 

The Electronics Industries Associ- 
ation CEIA), along with electronic- 
equipment manufacturers and re- 
tailers nationwide, launched a year- 
long public-service program at the 
1991 Winter Consumer Electronics 
Show to help Americans protect their 
hearing through the safe use of con- 
sumer electronics. Experts estimate 
that 28 million Americans suffer sig- 
nificant hearing problems, and that 10 
million of those suffer hearing loss 
due to excess noise. The ElA's "We 
Want You Listening For a Lifetime" 
campaign provides tips on safe 
equipment use and general informa- 
tion on potential hearing damage 
caused by playing sound systems at 
unsafe decibel levels. 

High-speed quantum FET 

A new device, developed by Valid 
Logic Systems CSan Jose, CA) engi- 
neer Gene Cavanaugh, is expected 
to surpass the 0.2 u,m technology 
that has been considered the prac- 
tical limit for conventional semicon- 
ductor technology Called the quan- 
tum FET, or QFET, the device 
potentially increases logic speed ten 
times, and simultaneously reduces 
power requirements and size by ap- 
proximately a factor of ten. Cav- 
anaugh has applied for a patent and 
has approached Texas Instruments, 
IBM, and Intel concerning possible 
licensing agreements to provide an 
opening for actual QFET production. 

The single-junction QFET's take 
advantage of "quantum tunneling," a 
physical phenomena that increases 
speed by eliminating the area of elec- 
tronic conduction in which carriers 
slow down by up to 3000 times. A 
manufacturing process called rapid 
thermal processing, or RTP, based on 
ultra-fine layers of material, is used. 
The device has potential applications 
in developing design-automation 
tools that benefit from high speed, 
low power, and small size. R-E 



SELECT 5 BOOKS 

for only $ 4^ 

(values to $117.75) 

Guaranteed 





SimpUJJeil 



3440P $17.95 



When it's new and important in business or personal computing, 

The Computer Book Club has the information you need , . . 

at savings of up to 50% off publishers' prices! 



JfllP S17.M 





3S7BP S 16.95 



3401 P 517.35 



3S54P $19.55 



Membership Benefits " Big Savings. In addition to this introductory 
offer, you keep saving substantially with members' prices of up to 50% off the 
publishers' prices. • Bonus Books, Starting immediately, you will be eligible for 
our Bonus Book Plan, with savings of up to BO% off publishers' prices. • Club 
News Bulletins. 1 5 times per year you will receive the Book Club News, describ- 
ing all the current selections — mains, alternates, extras— plus bonus offers and 
special sales, with scores of titles to choose from, • Automatic Order. If you want 
the Main Selection, do nothing and it will be sent to you automatically. If you prefer 
another selection, or no book at all, simply indicate your choice on the reply form 
provided. You will have at least 10 days to decide. As a member, you agree to 
purchase at least 3 books within the next 2 years and may resign at any time there- 
after. • Ironclad No- Risk Guarantee, If not satisfied with your books, return them 
within 10 days without obligation! • Exceptional Quality. All books are quality 
publishers' editions especially selected by our Editorial Board. 

©1991 THE COMPUTER BOOK CLUB Blu8 Ridge Summit. PA 17294-OB20 

All books are hardcover unless number is foflkwed by a "P" for paperback. (Publishes' Prices Shown) 



150C2P $32.95 



9335P $10-95 
CounCi at 2 



irni iTia ii hi i in BhA Jiiti 

~"V; Blue Ridge Summit, PA 17294-0820 



Please accept my membership In The Computer Book CJub and send the 5 volumes listed below, 
bitting me $4.95. If not satisfied. I may return the books within ten days without obligalion and 
have my membership cancelled. 1 agree lo purchase at least 3 books at regular Club prices 
during I he next 2 years and may resign any time thereafter. A shipping/handling charge and 
sales tax will be added lo all orders. 



Name . 
Address 

City 

State _ 



Zip 



Phone 



Signature , 

Valid lor new members only. Foreign applicants will receive special ordering instructions. Canada mus! remit 

in U.S. currency. This order subject lo acceptance' oy The Computer Book Club- RPIC&91 

1 I 




35G3P (22-35 



3176P S1S.95 



PDTLD TOO! OWM 

80386 

IBM COMPATIBLE 
AND SAVE A BUNDLE 







jn-Biiif riuatu 



3131 S26.95 
Counts as 2 



I i>i- HAJtfWCCK 

of naK5CCH>irji3i j 
HnmncMo A 

yttf 

a* 






-*sas 



31 DIP SI 9. 95 


SD049PS15.9S 


UHUHllMttf 


Building 
I I ibraries 

O 

m 





3656P 517.95 



541 flP 526.95 
Counts ■■ 2 




3- 



3ZS3 $28.95 
Count* *t 2 



341 5P 521.95 




3BEME 




What's new in the fast-changing video industry. 



• Low-cost captions. In a hurry- 
up effort to implement the recent 
Congressional mandate to include 
closed-caption decoders in all TV 
sets 13 inches and larger (Radio- 
Electronics, October 1990), a spe- 
cial Electronics Industries Associa- 
tion (EIA) task force recommended 
new parameters that would make de- 
coders inexpensive by building upon 
the on-screen character-generation 
systems already used in many sets. 
The EIA plan, which would decipher 
existing closed captions for the hear- 
ing impaired, formed the basis for an 
FCC rule-making proposal. Members 
of the task force said the proposed 
system might add $2 or $3 to the 
cost of a TV set. 

The EIA plan envisions certain 
compromises, making some cur- 
rently mandatory aspects of caption 
decoding optional. Those include a 
special full-screen "text" mode that 
isn't widely used at present, a second 
data channel, and captions in color. In 
exchange, the EIA proposes that 
Field 2 of Line 21 of the vertical blank- 
ing interval be opened up for a bet- 
ter — but optional — second channel, 
and that the captions be capable of 
location anywhere on the screen to 
avoid interference with material in the 
picture. 

The proposal was approved by all 
members of the EIA task force except 
the National Captioning Institute, 
which said its own system, currently 
in use, could also come down to the 
$2-$3 level when chips are available 
in large quantities from a variety of 
sources. The EIA plan possibly can 
be combined with another EIA project 
being explored by receiver- and cable- 
engineering interests. That is a stan- 
dardized "program identification sys- 
tem," which would make possible on- 
screen labeling of station call letters 
and program titles, along with such 
information as the running time of the 
program and how much more remains 
to be shown, at the push of a remote- 
control button. Ultimately, such infor- 
mation could be combined with auto- 
matically recording VCR's, to tape 
programs of specific interest — -for ex- 



ample, all non-scheduled news bul- 
letins, or all operas. 

The FCC was ordered by Con- 
gress to promulgate final closed-cap- 
tioning rules by April 12. New TV sets 
made or imported on July 1, 1993 or 
later must include caption de- 
coders — but some manufacturers 
are expected to add the decoders to 
their sets some time this year if the 
simplified ElA-proposed rules are 
adopted. 

• Digital HDTV. As in audio, "dig- 
ital" has become the magic word in 
high-definition TV systems. Most 
contenders for consideration as the 
American system now have shifted to 
digital systems, although detailed en- 
gineering plans still are scanty. Major 
digital systems now include those un- 
der development by the ACTV Con- 
sortium, consisting of Thomson, 
Philips, NBC, and the Sarnoff Re- 
search Center; the Zenith— AT&T 
combine; and General Instrument. 

In the latest development, the MIT 
team, which had proposed an analog 
system, is working with General In- 
strument on a combined digital tech- 
nology. There are some dissenting 
voices in the digital race, however. Dr. 
William Schreiber, formerly of MIT 
and a longtime TV authority who in 
the past has questioned the consum- 
er benefits of HDTV, has decried the 
"stampede" to digital systems at a 
time when digital transmission hasn't 
been proven practical. He warned 
that if all American proposals are dig- 
ital and digital transmission proves 
impractical, the 20-year-old Japanese 
system could be the winner in the 
U.S. by default. 

• Interactive video. The FCC has 

started a rule-making procedure to 
set aside frequencies for "interactive 
video data service" C1VDS), which 
could be used for pay-per-view sys- 
tems, home shopping, games, edu- 
cational programming, and even for 
programming VCR's. The Commis- 
sion proposes to allocate 500 kHz in 
the 218-MHz band to IVDS, and to 
license two operators in each service 



area to share in this service from 
home to TV station or cable system. 
One interactive proponent said that 
such a system could probably oper- 
ate much like cellular phone net- 
works, each cell site connecting up to 
10.000 homes by radio and being ca- 
pable of handling up to 600,000 mes- 
sages per minute. 

• Multimedia Computing. What 
is claimed to be the first mass-market 
computer with interactive multimedia 
capability will be manufactured by 
Emerson Technologies for Trac. At- 
lanta, and designed to sell for less 
than $2,000. The price breakthrough, 
according to Emerson, is the result of 
the availability of the "PC Video" chip 
developed by Chips & Technologies 
Inc.. San Jose, CA. That single-chip 
processor permits PC's to accom- 
modate input from VCR's, camcor- 
ders, TV sets, laser discs, and other 
video sources, for display on the 
monitor and storage in the PC's pro- 
gram. It will even let computer oper- 
ators watch and listen to on-screen 
newscasts while involved in other- 
wise serious labor. The PC Video 
chip initially is priced at $55 in volume 
and is claimed to reduce the cost of 
adding multimedia to computers by 
as much as 70%. 

• Instant Video. Ycu may not want 
to see a full-length movie in 15 sec- 
onds, but Explore Technology, of 
Phoenix. AZ. , thinks that's all the time 
that's needed to transmit it. Explore is 
proposing a pay-per-view system, 
based on its patent for data compres- 
sion, which permits transmission of 
programming in short bursts to a re- 
ceiver which stores the information 
briefly in memory, and then plays it 
back with the proper timing. Explore 
says the saving in transmission costs 
will make such programs competitive 
with video rentals. The system is said 
to be compatible with any transmis- 
sion medium, and includes a trans- 
mitter and receiver that can be 
connected by fiber, satellite, broad- 
cast, coaxial cable, or even phone 
lines. R-E 



Now, Testing 

68000/386SX 
Microprocessors 

Is A Snap. 




Nothing'? foster than the chips being 
; developed today, and nothing's slower than 
hand wiring or trying to analyze these high- 
^ ^ density, surface mounted quad flat pack (QFP) 
devices for test. No worry, Pomona has the answer. 

You can choose Pomona's 571 1 SMT Test Clip to 
grab onto all 132 pins of a Motorola 68020 or 68030, or 
the 5713, to simultaneously access all 100 pins of an Intel 
80386SX. Immediately, your interface with logic analyz- 
ers, on-line circuit test systems, or lab instruments will be 
faster, easier, and reliable. A locking mechanism firmly 
holds the glass-filled, Nylon insulated clip onto the 
device, making positive contact with each of the IC's 
gull-wing leads via specially configured, gold-plated, 
beryllium copper pins. Above, multi-rows of gold-plated 
phosphor-bronze pins provide an easy-to-access pattern. 
Suddenly, interface problems are solved. 



FREE 1991 POMONA 
CATALOG! l-10-pages of 
* newest prod 'nets and 
a», thousands of test solutions. 




5515A PLCC Clip Kit 
contains seven Pomona QuatP Clip 
Adapter from 20-84 pins. 




If you anticipate 
testing various pin- 
count PLCC or SOIC 
devices, Pomona's 
Test Clip Kits will make 
testing faster too. And, 

to make the interface between your test clip and logic 
analyzer sockets or emulator pods easier, Pomona's 
Flying Leads are available in low-cost packs, or sup- 
plied with the 5711 and 5713 Test Clips as kits. Of 
course, all of Pomona's other SMT test accessories are 
ready to make 
your IC testing 

faster and leSS " ^ Color-coded Flying Leads amplify 

expensive interconnections between PLCC or SOIC lest clip and 

* „ ' logic analyzer sockets or emulator pods; 3 inches 'long, with 
oCe yOUl" female socket one end to . 79 dia. pin. 

Authorized Pomona 25 to&.pirp&k 

Distributor or contact POMONA ELECTRONICS, 
1500 E. Ninth St., P.O. Box 2767, Pomona, CA 91769. 
(714) 623-3463. FAX (714) 629-3317. 




■&1& 



Nylon is a registered trader™* of DuPont 
CIRCLE 101 ON FREE INFORMATION CARD 



ITT Pomona 

AN ITT EMC WORLDWLDE COMPANY 

Discover our strengths. 



What's yoi 




Analyzing TV and complex video signals? 




Testing telecommunications signals? 




Uncovering elusive glitches? 



CHI 1U i, Zp, J. 56 u UE»I 

*fi !.»• U Itftnt CM. tall 






Finding aberrations buried within a signal? 

You can't depend on banner specs 
alone to solve problems like these. 

Whether you're trying to measure waveform 
parameters or analyze long data streams, 
identify infrequent events or track down 
glitches as narrow as 2 ns — there's all the 
difference between the depth of Tek 
troubleshooting and the trade-offs in other 
DSOs that compromise your results. 

Spec for spec, feature for feature, no other 
company offers the credentials Tek does to 




Capturing single-shot events? 



H 2e«|ii 3.72 U7 UEK 



«F1 1.6(1 V Zttpi 




AC4UKE I 32 ttftl SKUE OH 



Automatic PASS/FAIL testing? 

effectively match DSO performance to you 
application needs. Whatever your criteria, 
you'll find a perfect solution in our line of 
problem-solving portable DSOs, from 10 to 
500MS/S. 

Select the features to support your 
application. Tek DSOs offer a diverse set 
of capabilities including peak detect to 
uncover elusive glitches. Fast update rate fc 
live signal display. Combined analog/digits 
operation for real-time verification of your 



Copyright e 1990. Tekronii. Inc. AH rigliis reserved. BOB-125 



problem? 




Characterizing signal noise 1 



1-e.aiU IRM1-E.90 4l»l.B8iies 1 








,, • 




.••■ V 


_ _ 


n* m ** ff «* *q M M«l 




A 




„:..,., 1 



Capturing and analyzing long data streams? 



see»u 

CHI 590. u 

CHl> 


hi 

M.B9 

': 




► 


/ — r 







Measuring timing relationship between signals? 



SSnt 533. I* 'Itt- 



ft I06n. 2. 52 U UC*T ■ ■ CHI 2(1 1ft JOp« 2,54 U UERlH ■ CHI 50B.U 

e !■«>« 

■ 6.803(1Hi H' F1 Z . UO U iMnl iJB.COrn 

' UK ■ H,hl . „ , KEFl W10TH • 336m CHI UtttTjl I 



0* FUHCTH* 
UQLTS TIME VtT SLQfr 




niri ^ ' 



CUK5DK FUlttUOH 



rforming complex measurements automaticaUy? 



Expanding glitches for close analysis? 



gnal. Or Save on Delta to automatically verify that all parts 
f your signal fall within prescribed limits. Best of all, 
ek's line of 100 MS/s digitizing scopes start at just $3995. 
To find out which Tek scope is right for you, contact 
our Tek representative, return the card or call Tek 
irect. We can answer your questions and show you a 
xrpe that doesn't just look good on paper. It makes your 
Highest troubleshooting challenges routine. 

1-800426-2200* 



Windowing in on signal details? 



One company measures up. 





Tektronix 

cajwrrrcz] ruL«iuXNCS 



CIRCLE 92 ON FREE INFORMATION CARD 



ASK RE 



Write to Ask R-E, Radio-Electronics, 500-B Bi-County Blvd., Farmingdale, NY 11735 



o 

o 

cr 

i- 
o 

HI 



o 

G 
< 



PRINT-SCREEN INDICATOR 

I'd like to modify my IBM- 
style keyboard so it has an in- 
dicator to show when I'm 
using the print-screen func- 
tion. Ideally it should be some- 
thing similar to the caps lock, 
num lock, and scroll lock LED's 
that I currently have. Any 
ideas? — T. Waller, Yorktown 
Heights, NY 

What you're asking is one of those 
things that seem simple but is actu- 
ally quite complex. It's a kind of "Why 
is the sky blue?" type question. 

The first thing to understand is that 
the PC's keyboard is different from 
the ones used by Apples and a few of 
the other popular home computers. 
The first difference is that it's not a 
simple matrix keyboard in which each 
keypress connects two or more wires 
together to generate a series of highs 
and lows on a multi-pin connector. 
The PC keyboard is a serial device, 
and the standard five-pin connector 
carries the data, power, clock, 
ground, and reset signals on sepa- 
rate lines. 

The second difference becomes 
evident once you know of the first 
difference, since you can't generate 
serial data without a bunch of silicon. 
As a result, the PC keyboard is really 
a small computer in itself and, al- 
though different keyboard manufac- 
turers use different IC's, most of 
them base the keyboard circuitry 
around a microprocessor specifically 
designed to handle and control I/O. 
The 803X, 804X, and 805X micro- 



processor series from Intel is a fairly 
common choice. Figure 1 shows the 
inside of such a keyboard. 

Knowing those facts, you can see 
that what you want to do has to in- 
volve a lot more than piggybacking an 
LED onto a couple of switches. 

That isn't to say that what you want 
to do is impossible. It's an involved 
project and would more than likely 
require you to design some circuitry 
of your own. Keep in mind that, if you 
build something that sits inside your 
keyboard and monitors anything 
other than the output, you'll more 
than likely be able to use the device 
only on your own particular keyboard. 
Different keyboards use different cir- 
cuitry. There's not enough room here 
to go into the details of building a 
circuit like this but I can block out the 
approach that I would follow. 

There are two basic approaches to 
the problem. The first is to monitor 
the data going from the keyboard to 
the computer and the other is to cap- 
ture the particular combination of 
switch closures in the keyboard be- 
fore they reach the keyboard's con- 
troller. I'm not going to take a guess 
as to which would be easier but, if I 
was doing this, I'd choose the first 
alternative since I wouldn't want to 
take any chance of damaging the key- 
board circuitry. 

If you do want to modify the key- 
board itself, you could try to identify 
the combination of highs and lows 
sent on the keyboard's internal data 
bus whenever you do a Print Screen. 
Once you've found those, you could 




FIG. 1 — A PC KEYBOARD is a small computer in itself. This keyboard's circuitry is based 
on an 8048 microcontroller that's specifically designed to handle and control I/O. 



buffer and decode them to drive an 
indicator such as an LED. 

CABLE TRACER 

I'd like to trace the path of an 
underground power cable. 
One end is above ground and 
the other end is lost some- 
where below ground. Neither 
end is connected to power. 
Isn't there some sort of wave 
generator I could build that 
would provide a signal I could 
trace with a receiver and an- 
tenna? — D. Andrew, British 
Columbia, CA 

It's really terrific when a simple 
question like this has a really simple 
answer. I've faced this problem my- 
self and I'll pass along the method I 
used. 

Most of the commercial equipment 
that's designed for this purpose 
works exactly as you described. A 
signal is sent along the wire and a 
specially tuned receiver picks it up. 
Depending on the amount of bells 
and whistles, that sort of gear can set 
you back an impressive number of 
bucks. But there's an alternative. 

As long as you're sure that both 
ends of the cable aren't connected to 
anything, connect the above-ground 
end to the 120VAC line (through a 
fuse and ground-fault protector). 
Once you've done that, connect the 
noisiest appliance you have to the line 
and turn it on. The best ones to use 
are those with motors that have a set 
of old brushes in them. You can usu- 
ally spot that by seeing whether lots 
of sparks are created where the 
brushes ride on the motor. 

Each one of the sparks is generat- 
ing a lot of RF noise that's being 
transmitted down the cable. You can 
detect the noise with a portable radio 
since the noise spreads across a 
wide band of the spectrum. All you 
have to do is tune the radio between 
stations (you may find the AM band is 
better), turn up the volume, and fol- 
low the static across the ground. This 
may seem a primitive method but it's 
exactly the method used by the "high 
priced spread." 



12 



KEYBOARD UPGRADE 
How can I make a 101 -key 
keyboard from an IBM AT op- 
erate with an IBM-compatible 
WYSE PC+ model WY-1400- 
20? I would be willing to build 
some simple circuitry if it's 
necessary.— B. Van de Ayr, 
Chehalis, WA 

While there's probably no reason 
why you can't do what you want, 
there are a few problems in getting it 
done. I'm not familiar with either the 
Wyse-PC+ or its keyboard but, just 
because the computers are compati- 
ble, there's no guarantee that the key- 
boards are compatible. (There are 
different degrees of compatibility.) 
Not all models of IBM keyboards are 
interchangeable with each other. The 
keyboards designed for the XT, for 
example, will not work with the AT. 

If you're dead set on modifying or 
adapting the Wyse keyboard for use 
with your AT-compatible computer, 
you'll need some very specific infor- 
mation before you can get started. 

• You need a list of the scan codes 
produced by the Wyse keyboard and 
those required by the AT-compatible. 

• You need a schematic of the Wyse 



keyboard that shows, among other 
things, the pinouts of the output con- 
nector and how the data is transmit- 
ted to the computer. 

• Although not strictly necessary, 
make sure the scan codes for the 
extended function keys(F11 and F12) 
are compatible with the IBM. 

• Be certain that both the power and 
reset requirements of the Wyse key- 
board can be supplied by the IBM. 

There's one other thing to be aware 
of since you're trying to use the key- 
board with an AT, rather than an XT. In 
AT-class computers, the data from 
the keyboard is handled by a pre- 
programmed microcontroller in the 
computer itself. There are a few com- 
panies (Phoenix, AMI, etc J that can 
supply that, but they are not all com- 
patible with each other. That is usually 
a consideration only for setting the 
CMOS configuration memory of the 
computer, but keep in mind. 

Adapting the Wyse keyboard may 
turn out to be something as trivial as 
changing the connector on the end of 
the cable but. considering the fact 
that you can buy a keyboard for about 
fifty bucks, you have to wonder it's 
really worth the effort. R-E 



Try the 

MZBEntnmics 

bulletin board 
system 

(RE-BBS) 
516-293-2283 



The more you use it the more 
useful it becomes. 

We support 300 and 1200 baud 
operation. 

Parameters: 8N1 (8 data bits, no 
parity, 1 stop bit) or 7E1 (7 data 
bits, even parity, 1 stop bit). 

Add yourself to our user files to 
increase your access. 

Communicate with other R-E 
readers. 

Leave your comments on R-E with 
the SYS0P. 

RE-BBS 
516-293-2283 



Be an FCC 
LICENSED 

ELECTRONIC TECHNICIAN! 




Earn up to 
$30 an hour 
and more! 



JiJ 



.rn at home in spare time, 
previous experience needed! 



No costly school. No commuting to class. 
The Original Home-Study course prepares 
you for the "FCC Commercial Radio- 
telephone License" This valuable license is 
your professional "ticket" to thousands of 
exciting jobs in Communications. Radio- 
TV, Microwave, Maritime, Radar, Avionics 
and more... even start your own business! 
You don't need a college degree to qualify, 
but you do need an FCC License. 
No Need to Quit Your Job or Go To School 
This proven course is easy, fast and low 
costl GUARANTEED PASS— You get your 
FCC License or money refunded. Send for 
FREE facts now. MAIL COUPON TODAY! 

" commdND "productions" " 

FCC LICENSE TF1AINING, Dept. 90 
P.O. Box 2824, San Francisco, CA 34126 
Please rush FREE details immediately! 



ADDRESS . 
CITY 




Made in the U.S. A. 

Building the best DMM for [lie money is no 
accident The new RMS225 was carefully 
desigied to give you what you wanted at a price 
you could afford. Visit your local distributor 
today and you'll agree die choice is obvious. 



Fluke 
Model 77 


Beckman Industrial 
RMS22S 


3->A Digits 


4 Digits 


3,200 Counts 


10,000 Counts 


0.3% Accuracy 


0.25% Accuracy 


Touch Hold 9 


Prone Hold™ 


31 Segment Analog 
Bar Graph 


41 Segment Analog 
Bar Graph 


2,000 Hour Battery Life 


1,000 Hour Battery Lite 


10A Range fam 


10A Range (fumi 


Protective Holster 


Protective Holster 


3 Yr. Warranty 


3 Yr. Warranty 


True RMS 


Auto Mln Max™ 


Relative Mode 


$159' 


SW9 


' s Touch Hold is a registered trademark of the John Fluke 
Mfg. Co., Inc. "1990 Hoke and Philips Catalog 

Beckman Industrial" 



An AiUhate of Emerson Electric Co 

Instnimenutlton Producis Division 

3883 Ruffin Road, San Diego, CA 92123-1890 

(619) 495-5200 - FAX (619) 268-0172 ■ TLX 249031 

Outside California 1-800-854*2708 vViihin California 1-800-227-9781 
© 1990 Bcdanin Industrial 1 Corporation Specif jcukais subject to diangc 
without notice. Flute is a ngjirwl tnotm&A of John Flute Mfe Cci. lnc 

JHl^O-G 1-Q59I 

CIRCLE 98 ON FREE INFORMATION CARD 



£ 
$ 



13 



mm 



Call (800) 992-9943 

Over 35,000 
Electronic Components 

Call Today for Your 
FREE SUBSCRIPTION 

If You Order Today, 

WE SHIP TODAY!! 




Stocking Locations Across America. 



CIRCLE 117 ON FREE INFORMATION CARD 



LETTER5 



Write to Letters, Radio-Electronics, 
500-B Bi-County Blvd., Farmingdale, NY 11735 



MAC PLUS FIX 

I would like to thank Radio-Elec- 
tronics for the fine article on build- 
ing a Mac clone (January 1991), My 
Mac Plus nuked itself last week. I 
removed the power board and. upon 
taking the board to two Apple deal- 
ers , I was told that it would cost $300 
to fix — and I would have to put the 
board back in the Mac and then bring 
them the whole machine. No way! I 
opened the magazine and called Pre- 
Owned Electronics. They sent me the 
board in two days for $119. I want to 
thank you guys forall the help in locat- 
ing decent merchants who want to do 
honest business. Keep up the good 
work. 
RICHARD RUSSO 

TABLE THAT TABLE! 

I read the article "1 Volt = ?" (Ra- 
dio-Electronics, February 1991) 
with considerable interest. It was well 




I 




en 
g 

z 
o 
cr 
i- 
o 

LU 



O 

□ 
< 

IX 



14 




A 1 Makey. servicing 

K ft/*^ *^ * problems disappear u 

fli%4 ■ fn "' l lo trace with the latest 

^^\rV^C^. M f^Ak^ from the eomp 

17 lliL*^\l video servicing ben kila. 

\ ^S Fifth in a series of service bulletin 

» compilations, the SB-09 features ninety-five pages 
of valuable troubleshooting information for populi 
and Qua*. ncr cameras, camcorders and video cass' 

ders manufactured between 1983 and 1990. 

To order you r SB -0.' '■' ') eck or money order for # 

i lering from NJ ) to the address below. 7 
amounts include shipping and handling charges, and l 
applu -.n elude a copy of this ad 

with your order. A How 4 -8 weeks for 

■ CD's, 

charg 

Reo 

serv lids by M 

Matsushita 

Services Company 

fochnlcal A d /?■ Doc. 



ita! 



IdcltC^U^iJ} Bd^L 



imm 




written and comprehensive. It con- 
tained a gratifying amount of basic 
physics and pulled together a great 
many ideas that are often hard to find 
because they are scattered over sev- 
eral different chapters in various text- 
books. 

Were it not for one fundamental 
flaw. Table 1 would be an extremely 
useful reference for students of sev- 
eral academic disciplines. The author 
used an obsolete and (now) non- 
standard set of base Cor principal) 
quantities. 

Intellectually and philosophically I 
like the author's choice of charge as a 
base unit and his derivation of dimen- 
sional equivalents in terms of cou- 
lombs. I also still "like" to use mhos, 
micro-microfarads, milli-microamps, 
and kilo-megacycles. Nevertheless, 
those outdated standards are all con- 
trary to the American National Stan- 
dards that have been in effect for 
some time now and really are the 
ones that should be used. 

If the author and your editors would 
check the IEEE Dictionary for "units 
and letter symbols," I believe they will 
find that the electric base quantity (in 
the SI system) is current, not charge. 
Charge is now properly described as 
a "derived" quantity that has dimen- 
sions of (current x time) or ampere- 
seconds. Regrettable, that means 
that in each of the author's "Dimen- 
sional Equivalents" in Table 1, the 
Coulomb (C) term should be re- 
placed with (A x s), and the terms re- 
collected. 

I know this all seems perverse to 
old-timers who learned to start with 
the charge on the electron and to 
calculate how many electrons it takes 
to make a coulomb, but there is a 
good practical reason for the change. 
When you use current as the base 
unit for electrical measurement, you 
can define the ampere in terms of the 
force exerted upon two parallel con- 
ductors. That is evidently something 
that is more directly measurable in 
terms of mass, length, and time — and 
more up-to-date. 
LUCIUS DAY 
Lakewood, CO 



CIRCLE 190 ON FREE INFORMATION CARD 



REMOVING IC'S 

Thank you for the years of excel- 
lent reading in the extremely diverse 
field of electronics. I've been reading 
Radio-Electronics on and off for 
some years, and have enjoyed every 
issue. 

Now for the good news. Over the 
years I have read letters from readers 
about the handling of IC's and the 
questions concerning their abuse. 
Well, here is some shocking news. 
When chips CTLL's, CMOS, etc.) are 
manufactured, they are dipped in a 
molten material. Notice I said molten, 
which means that the material is in 
liquid state. The material used and 
the temperature of that material must 
give off heat during the change of 
state from liquid to solid. Thinking 
about that concept, I began to work 
on a way to extract circuit-board com- 
ponents without the use of desolder- 
ing tools, and one that would save 
plenty of time. 

Try this out for size: Using a hot oil 
bath as a desoldering fluid and keep- 
ing the temperature down to a level 
that the IC's could handle, I dropped 
the board in, and within seconds 
parts began to fall off the board. The 
temperature of the oil bath should be 
no lower than 370°F and no hotter 
than 380°F. That temperature is with- 
in an IC's tolerance. 

The only exception is electrolytic 
capacitors, as they will explode and 
send hot oil all over the place. 

Use gloves and eye protection dur- 
ing this process. I have extracted hun- 
dreds of useful parts that way and 
have had an 80% success rate. I said 
80% because some plastics cannot 
withstand that temperature, and the 
hot oil can break down some plastics 
altogether. 

1 hope your readers can use this 
information— but if you do, be sure to 
observe safety first. And thanks 
again for the excellent reading materi- 
al. Keep up the good work. 
MICHAEL BROWN 
Stockton, CA 

Your method sounds a tittle dan- 
gerous to us, but it does show that 
where there 's a will, there s a way! — 
Editor 

AM PROBLEMS 
Since Radio-Electronics 

printed the article "Whatever Hap- 
pened to AM Radio" (September 
1990), I thought the editors and read- 
ers might be interested in the reply I 



received from my congressman in re- 
ply to my suggestion that AM stereo 
circuitry be mandatory in future AM/ 
FM stereo equipment. Congressman 
Dale E. Kildee said, in part, "In recent 
years, new technologies have been 
employed that have led to a wider use 
of AM stereo components. At this 
time, no legislation has been intro- 
duced in the House of Represen- 
tatives that would require stereo 
manufacturers to place AM stereo 
components in their equipment." 

All three AM-only radio stations in 
my area were sold at bargain prices 
last year — one at auction, one in 
bankruptcy court, and one to a 
church. Only the latter, a gospel sta- 
tion, emerged with no major 
changes. The first, which was a lead- 
ing Top-40 station in the 60's and 
70s, became a Christian station 
whose last Arbitron rating was 0.0. 
The second, formerly the leading 
news and information station, switch- 
ed to a satellite-fed, heavy- metal rock 
format called "Z-Rock." Despite 
adding AM stereo equipment, the 
station was not successful, and went 
off the air. The owner (who also owns 
a mobile-home sales lot and added 
another one on the radio-station 
grounds) plans to try another format, 
but as of this writing the station is still 
off the air. 

It would appear that your article is 
right on the mark concerning AM ra- 
dio's problems. 
GARY FLINN 
Flint, Ml 



WRIST STRAPS 

Steve Swenton's statement on 
using a wrist strap when desoldering 
static-sensitive devices (Letters, Ra- 
dio-Electronics, September 
1990), "...always use a ground strap 
(a metal wrist strap with a detachable 
ground wire) and connect its wire to 
ground,..," needs further clarifica- 
tion, lest someone fashion a home- 
made wrist grounding strap from that 
description. 

Commercially available wrist 
strap/ground wires contain a current- 
limiting resistor, usually 1 megohm, in 
order to protect the operator. One 
should never connect oneself to a 
hard ground when working around 
sources of potentially lethal (e.g., 
household) current, 
JOHN L. HORNBY 
Madison, CT 



Earn Your B.S. Degree 

in 

ELECTRONICS 

or 
COMPUTERS 




By Studying at Home 

Grantham College of Engineering, 
now in our 41st year, is highly ex- 
perienced in "distance education" — 
teaching by correspondence— through 
printed materials, computer materials, 
fax, and phone. 

No commuting to class. Study at 
your own pace, while continuing on 
your present job. Learn from easy-to- 
understand but complete and thorough 
lesson materials, with additional help 
from our instructors. 

Our Computer B.S. Degree Pro- 
gram includes courses in the BASIC, 
PASCAL, and C languages — as well 
Assembly Language, MS DOS, CADD, 
and more. 

Our Electronics B.S. Degree Pro- 
gram includes courses in Solid-State 
Circuit Analysis and Design, Control 
Systems, Robotics, Analog/ Digital Com- 
munications, and more. 

An important part of being pre- 
pared to move up is holding the right 
college degree, and the absolutely neces- 
sary part is knowing your field. 
Grantham can help you both ways — 
to learn more and to earn your degree 
in the process. 

Write or phone for our free 
catalog. Toll free, 1-800-955-2527, or 
see mailing address below. 



Accredited by 

the Accrediting Commission of the 

National Home Study Council 



GRANTHAM 

College of Engineering 

Grantham College Road 
Slidell, LA 70460 



I 



15 



XT-TO-AT UPGRADE 

Having worked for a company that 
manufactures floppy disks, I'd like to 
make several comments concerning 
the differences between various disk 
formats. 

It's true that 5'/i-inch, high-density 
CI .2 MB) drives have twice as many 
tracks as the regular 360K drives. 
That doesn't increase the chance of 
crosstalk, however, because the 
track width (the width of the track 
written or read by the head) is, of 
course, also half as great. 

tt isn't a case of the write current 
being decreased on high-density 
(HD) drives. Instead, the write field is 
increased. That is necessary be- 
cause there is a fundamental dif- 
ference between disks designed for 
HD operation and non-HD operation: 
The HD disks' coating material needs 
a ri/g/ierfield to reliably saturate (i.e., 
be fully magnetized one way or the 
other). 

The software on an AT can change 
the write current on an HD drive. 
There's a pin specifically for that on 
the drive interface, and the BIOS can 
flip it when required. Indeed, it has to 
reduce the write current when writing 



to 360K disks because otherwise the 
excessive write field would cause 
each transition, as it was being writ- 
ten, to affect the previously written 
transition. 

The recorded level may seem low 
when reading on a 360K drive a disk 
written on a 1.2-MB drive, but that is 
because only one-half the normal 
track width has been written, causing 
a reduced signal output of approxi- 
mately 70%. I have never had any 
problems from that, since drives are 
rated to work with dropouts to 45% 
remaining signal and below. However, 
it is true that the loss of signal level 
does reduce your operating margin 
against problems like misalignment 
and drift. Of course, HD drives are 
rated to work with 360K-formatted 
disks despite the reduction in avail- 
able signal level. 

Where problems most often arise 
is when disks are overwritten by a 
succession of different drives. Re- 
member that HD drives can write only 
half-width tracks (relative to a 360K 
drive). So if a track is written "wide" 
and overwritten "narrow," a "wide- 
reading" drive will read both the new, 
wanted, narrow track and the rem- 



nant of the old wide track together. 

Remember that the directory area 
of the disk is rewritten whenever you 
add a file! The above problem may 
render every one of the files on the 
disk inaccessible from the addition of 
a single file, because the entire direc- 
tory has been corrupted. 

For the sake of completeness, I 
should mention that, while 3'/s-inch 
HD disks have a different material 
from regular (720K) 3'/2-inch disks, 
there is no difference in track widths, 
ruling out the problem of overwriting. 
Also, the coating materials are similar 
enough that a 720K diskette can 
often be formatted for 1 .44 MB with- 
out any errors reported during the 
format. However, the non-HD disks 
are highly marginal with the HD for- 
mat, and you are highly likely to en- 
counter reliability problems. Recent 
1.44-MB systems have implemented 
a sensor that detects the HD hole to 
prevent non-HD disks form being in- 
correctly formatted. It is probably 
also undesirable to format 3'/2-inch 
HD disks as 720K. but I haven't 
checked into that. 
DANNY WILLIS 
Munich, Germany 



o 

z 
o 

d 

I- 
o 

UJ 

_i 

LLJ 

o 

< 

DC 




EARN YOUR 
Dibit it , 

DEGREE 

THROUGH HOME STUDY 

Our New and Highly Effective Advanced- PEace- 
roent Program for experienced Electronic Tech- 
nicians grants credit for previous Schooling and 
Professional Experience, and can greatly re- 
duce the time required to complete Program and 
reach graduation. No residence schooling re- 
quired for qualified Electronic Technicians. 
Through this Special Program you can pull all ol 
the loose ends of your electronics background 
together and earn your B SEE. Degree. Up- 
grade your status and pay to the Engineering 
Level. Advance Rapidly! Many Ifnish in 12 
months or less. Students and graduates in aJ 50 
States and throughout the World. Established 
Over 40 Years! Write for fre* Descriptive Lit- 
erature. 



COOK'S INSTITUTE 

OF ELECTRONICS ENGINEERING 

4*£(VE: 435! CYPRESS DRIVE 
*s£'-*.E JACKSON, MISSISSIPPI 39212 



16 CIRCLE 58 ON FREE INFORMATION CARD 



JAN CRYSTALS 



your reliable source for 

a world of crystal clear 

communication 



• Commercial Two-Way 

• Microprocessors 

• Amateur/Experimental 

• Scanners/Monitors/Pagers 

• Satellite-Telemetry 

• Plus custom applications 

EXPEDITED ORDER SERVICE! 

FOR FREE CATALOG, 
CALL OR WRITE: 

JAN CRYSTALS 

P.O. Box 06017 
Ft, Myers, FL 33906 

(813) 936-2397 

TOLL FREE 1-800-526-9825 

FAX ORDERS: 1-813-936-3750 



VISA 



CIRCLE 104 ON FREE INFORMATION CARD 




CIRCLE 108 ON FREE INFORMATION CARD 



HOW MUCH SHOULD YOU PAY FOR 

10 INSTRUMENTS, 39 FUNCTIONS 

AND 4000 COUNT ACCURACY? 

Just $139.95 if you say PROTOMETER ! 

[Tj DC VOLTMETER 
[2] AC VOLTMETER 
[Tj OHMMETER 
[Tj 20A AMPMETER 
[Tj DIODE/LED TESTER 
\±\ TRANSISTOR TESTER 
\T\ CAPACITANCE TESTER 
[Tj FREQUENCY COUNTER 
{9} LOGIC PROBE 
[10) CONTINUITY TESTER 




PROTOMETER™ 4000 is the 
Professional Multi-Function Por- 
table Instrument System. Ten test 
instruments in a 3-3/4 Digit, 4000 
count handheld package. Pack- 
ing the power of our complete 
instrument line. Combining a digi- 
tal multimeter, frequency counter, 
transistor/capacitance tester, and 
more into a durable no-nonsense 




=SSV Cal1 Toil-Free For Details 

1-800-572-1028 



drop-resistant case. Plus standard 
features like a large LCD display, 
peak hold, and a unique high-volt- 
age warning indicator. Looks like 
the competition's DMM and priced 
like one too! 

GLOBAL 
SPECIALTIES 

CIRCLE 192 ON FREE INFORMATION CARD 



But PROTOMETER™ 4000 is 
much more than a DMM. Com- 
pare for yourself. Clearly the best 
value in portable instruments. Why 
pay just as much for a DMM, when 
you can get ten test instruments 
for one low price. How much should 
you pay? Just $1 39.95, if you say 
PROTO METER™ 4000. 

Order Yours Today!! $1 39.95 

Global Specialties' A028 

70 Fulton Terrace. New Haven. CT 06512 

Telephone :(203) 624-3 103, ©Interpleji Electronics, 1991 



S 



CO 

to 



17 



No other training— 

anywhere— shows you 

service computers 



Now includes 

AT-compatible, 

20 meg hard drive, 

and exciting new 

diagnostic package! 



Only NRI walks you through the 

step-by-step assembly of a 

powerful AT-compatible 

computer system you keep — 

giving you the hands-on 

experience you need to work 

with, troubleshoot, and service 

all of today's most widely used 

computer systems. With NRI at-home training, you get 

everything you need to start a money-making career, 

even a computer service business of your own. 



No doubt about it. The best way to 
learn to service computers is to 
actually build a state-of-the-art 
computer from the keyboard on up. 
And that's just what you do when 
you train with NRI. As you perform 
key tests and demonstrations at 
each stage of assembly, you see for 
yourself how each part of your 
computer works, what can go 
wrong, and how you can fix it. 

Only NRI, the leader in career- 
building electronics training for 
more than 75 years, gives you such 
practical, real-world computer 
servicing experience. Indeed, no 
other training — in school, on the 
job, anywhere — shows you how to 
troubleshoot and service computers 
like NRI. 

You get in-demand 

computer skills as you 

train with a powerful 

AT-compatible computer 

system — now with 1 meg 

RAM and 20 meg hard drive 

With NRI's exclusive hands-on 
training, you actually build and 
keep the powerful new AT-compat- 
ible West Coast 1010ES computer, 
complete with 1 meg RAM and 20 
meg hard disk drive. 

You start by assembling and 
testing the "intelligent" keyboard, 



move on to test the 
circuitry on the main 
logic board, install the 
power supply and 
5-^" highnJensity 
floppy drive, then 
interface your high- 
resolution monitor. But 
that's not all. 

Your NRI hands-on 
training continues as 
you install a powerful 
20 megabyte hard disk 
drive — today's most- 
wanted computer 
peripheral — included 
in your course to dra- 
matically increase your 
computer's data storage 
capacity while giving 
you lightning-quick 
data access. 



DIGITAL 
MULTIMETER 

Professional test 
instrument for 
quiet and 
easy circuit 
measurements. 



+A gg* 



HARD DISK DRIVE 

Tne 20 megabyte hard 
disk drive you install 
internally gives you 
greater data storage 
capacity and access 
speed. 



AT-COMPATIBLE 

COMPUTER 

80286 CPU (12 MHZ dock, 
wait sales), I meg RAM 
(expandable to 4 meg), 
1.2 meg hiijHlin-.il', 
floppy disk drive. 




LESSONS 

Gearcut, illustrated 
texts build your 
understanding of 
computers siep by 

sup. 



SOFTWARE 

kam to use MS-DOS, 
GW-BASIC, and the 
popular new Microsoft' 
Works integrated 
software package. 





New! Training now includes 

Ultra-X diagnostic 

hardware and software 

for quick, accurate 

troubleshooting! 



Now NRI takes your hands-on 
computer servicing experience an 
important step further: Now you 
train with and keep the remarkable 
R.A.C.E.R. plug-in diagnostic card 
and QuickTech diagnostic software 
from Ultra-X — professional diagnos- 
tic tools that make computer 
troubleshooting fast and accurate. 

Using these state-of-the-art 
tools, you learn to quickly identify 
and service virtually any computer 



in school, on the job, 
how to troubleshoot and 
likeNRI 



MONITOR 

High-rcsoluTion, 
rtrnglarti 12' TTL 
monochrome monitor 
wilh till and swivel 
base. 



TECHNICAL 



You get "inside* your 
AT-compatiblc 
computer system with 
exclusive NRI Training 
Kit Manuals plus 
technical specs direct 
from the mamifoaurer. 



DISCOVERT LAB 

Complete 

breadboaniing system 
to let you design inJ 
modify circuits, 
diagnose and repair 
faults. 





DIGITAL LOGIC 

PROBE 

Using your logic probe. 

you get firsthand 

experience inatyting 

digital circuit 

operation. 



problem on XT, AT 80286/80386, 
and compatible machines. You 
discover how to use the R.A.C.E.R. 
card to identity individual defective 
RAM chips, locate interfacing 
problems, and pinpoint defective 
support chips. Plus you learn to use 
your QuickTech diagnostic soft- 
ware to test the system RAM and 
such peripheral adapters as parallel 
printer ports, serial communica- 
tions ports, video display memory, 
and floppy and hard disk drives. 

Only NRI gives you such confi- 
dence-building, real-world experi- 
ence. Only NRI gives you both the 

knowledge and the professional 
tools to succeed as today's in- 
demand computer service technician. 



No experience 

needed... 
NRI builds it in 

You need no previous 
experience in comput- 
ers or electronics to 
succeed with NRI. 
You start with the 
basics, following easy- 
to-read instructions 
and diagrams, moving 
step by step from the 
fundamentals of 
electronics to sophisti- 
cated computer 
servicing techniques. 

With NRI's unique 
Discovery Learning 
Method, you're sure 
to get the kind of 
practical, hands-on 
experience that will 
make you fully pre- 
pared to take advan- 
tage of every opportu- 
nity in today's top- 
growth computer 
service field. 



You learn at your own conve- 
nience, in your own home. No 
classroom pressures, no night 
school, no need to quit your present 
job until you're ready to make your 
move. And all throughout your 
training you've got the full support 
of your personal NRI instructor and 
the entire NRI technical staff, always 
ready to answer your questions and 
help you achieve your training goals. 

Your FREE 
NRI catalog tells more 

Send today for your free, full-color 
catalog describing every aspect of 
NRI's innovative computer training, 
as well as hands-on training in video/ 
audio servicing, telecommunications, 
industrial electronics, and other 
growing, high-tech career fields. 

If the coupon is missing, write 
to NRI School of Electronics, 
McGraw-Hill Continuing Education 
Center, 4401 Connecticut Avenue, 
NW, Washington, DC 20008. 

AT is a registered trademark of International Business 
Machines Corporation. R.A.C.E.R. and QuickTech are 
registered trademarks of Ultra-X, Inc. 



SEND TODAY FOR FREE CATALOG 



r Schools mt 

McGraw-Hill Continuing Education Center *i'fl 

4401 Connecticut Avenue, NW T Washington, DC 20008 l.fl I 

^ CHECK ONE FREE 
CATALOG ONLY 



For career courses 
] approved under Gl Bill, 
check for details. 



□ 

D Microcomputer Servicing D 

□ TV/Video/Audio Servicing □ 

□ Telecommunications O 
D Industrial Electronics &. Robotics Q 

□ Security Electronics n 

□ Electronic Music Technology □ 
D Basic Electronics d 



Computer Programming 

PC Systems Analysis 

PC Software Engineering Using C 

Desktop Publishing & Design 

Word Processing Home Business 

Paralegal 

Ftction/Nonfiction Writing 

Automotive Servicing 



□ Building Construction 

D Air Conditioning, Heating, 

& Refrigeration 
D Electrician 
D Small Engine Repair 
G Locksmithing 

□ Bookkeeping & Accounting 



Nunc 


(please print) 


Age 


Address 


City/State/Zip 


Accredited Member, National Hume Study Council 


1-051 



CATV-RF SIGNAL ANA- 
LYZER. The FS74A Chan- 
nelizer Sr, from Sencore 
includes an exclusive, all- 
channel, microprocessor- 
controlled tuner for testing 
all standard and cable 
channels to FCC accuracy, 
including the return chan- 
nels, sub-band, off-air VHF, 
UHF, and FM. By selecting 
FCC. HRC. or ICC carrier 
shift tuning, the user can 
simply dial in the channel 
and read the video or audio 
signal level displayed in mi- 
crovolts or dBmV on the 
fully-autoranging meter. 
The FS74A also allows the 
user to analyze the audio/ 
video ratio on any channel 
without calculations, by 
setting the function control 
to the A/V position and 
reading the ratio in dB. 

Sencore's patented on- 
channel automatic signal- 
to-noise ratio test elimi- 
nates time-consuming sig- 
nal comparisons and cal- 
culations that are usually 
required when referencing 
noise on an unused chan- 




CIRCLE16 0N FREE INFORMATION CARD 



nel. Another patented fea- 
ture, the automatic dB- 
h urn- level test, measures 
hum on any modulated 
channel, and measures AC 
and DC volts through the 
RF input jack. The built-in 
digital voltmeter also can 
be used to measure AC 
and DC voltage, as well as 
ohms. The unit's built-in 
wideband (4-MHz) video 
monitor shows picture- 
quality and sync-compres- 



sion problems. For porta- 
ble use, the signal analyzer 
can be powered by two 
field-rechargeable bat- 
teries. A carrying case, 
strand hook, and IEEE 488 
and RS-232 interfaces are 
available as options. 

The FS74A Channelizer 
Sr. TV-RF signal analyzer 
costs $3495. — Sencore, 
Inc., 3200 Sencore Drive, 
Sioux Falls, SD 57107; 
Phone: 1-800-SENCORE. 



LOGIC ANALYZER. De- 
signed for applications in 
circuit design, digital test- 
ing, ATE development, edu- 
cation, microprocessor de- 
sign and debugging, and 
logic analysts. Rapid Sys- 
tems' R3800 logic analyzer 
features 16K data buffers 
for each of 32 input chan- 
nels, allowing users to cap- 
ture long, high-speed dig- 
cg ital signals at a 100-MHz 
2 sample rate. Powerful PC- 
g based software simplifies 
£ setup and measuring, and 
4j provides selectable sample 
£ rates to 100 MHz. The 
5 R3800 also offers complex 
ir triggering with a sequence 



of four 32-bit data patterns, 
trigger delay of up to 64K 
clocks, four trigger levels 
with data qualifiers, and a 
zoom-display function. It 
can load, save, and print 




CIRCLE 17 ON FREE 
INFORMATION CARD 



displays and files and can 
list in Hex, Bin, ASCII, or 
Dec. 

The R3800 32-channel 
logic analyzer costs 
$3995 —Rapid Sys- 
tems, Inc., 433 North 
34th Street, Seattle, WA 
98103; Phone: 

206-547-8311; Fax: 
206-548-0322. 

PORTABLE VIDEO 
FRAME GRABBER. With 
a low-power design that al- 
lows it to operate for up to 
ten years on a single 9-volt 
lithium battery, Portable 
Technologies' PFG-1 pro- 
vides a portable, conve- 



nient, and affordable way to 
do gray-scale image cap- 
ture from live video 
sources. The unit is contin- 
uously powered and ready 
for frame-grabbing at any 
time. The resultant image 
has a resolution of 
320x320 pixels with 64 
levels of gray. Square pixels 
are obtained with standard 
NTSC or RS-1 70 video sig- 
nals from video cameras, 
camcorders. VCR's, or TV 
monitors. 

The PFG-1 can digitize 
and store a video frame in- 
dependently in Veo of a sec- 
ond. The captured image is 
stored in internal memory 
until overwritten by another 
frame grab. The stored im- 
age can be transferred to 
any computer equipped 
with a standard RS-232 in- 
terface. There are no add- 
on cards to install. Frame 




CIRCLE 18 ON FREE 
INFORMATION CARD 



grabbing can also be initi- 
ated under computer con- 
trol via the serial interface. 
The frame grabber 
comes with PGRAB soft- 
ware, which runs on IBM- 
PC and compatible com- 
puters with CGA, EGA, or 
VGA and at least 128K of 
RAM. The software allows 



22 



Elelctninics, DTfDDDTlD 






THE MODEL WTT-20 IS ONLY THE SIZE OF 

A DIME, yet transmits both sides of a tele- 
phone conversation to any FM radio with 
crystal clarity. Telephone line powered - never 
needs a battery! Up to '/< mile range. Adjusta- 
ble from 70-130 MHZ. Complete kit $29,95 
+ $1.50 S + H. Free Shipping on 2 or more! 
COD add $4. Call or send VISA, MC, MO. 
DECO INDUSTRIES, Box 607, Bedford 
Hills, NY 10507. (914) 232-3878. 

CIRCLE 127 ON FREE INFORMATION CARD 




COMPUTER KITS, BOARDS & COMPO- 
NENT PARTS. Designed to the highest de- 
gree of quality and reliability available today. 
They're fun, easy to build, educational, IBM 
compatible, very powerful, and at great 
prices. All items are pre-tested, include a full 
year warranty, step by step assembly manual, 
and free tech support. Assembly available at 
no extra charge. For free catalog contact: 
GENERAL TECHNICS, P.O. BOX 2676, 
LAKE RONKONKOMA, NY 11779, or call 
(516) 981-9473. VISA, MasterCharge, Ameri- 
can Express, COD. 

CIRCLE 176 ON FREE INFORMATION CARD 




FREE CATALOG! ELECTRONIC TOOLS & 
TEST EQUIPMENT. Jensens new Master 
Catalog, available free, presents major brand 
name electronics toois, tool kits, and test in- 
struments, plus unique, hard-to-find products 
for assembly and repair and custom field ser- 
vice kits available only from Jensen. All fully 
described and illustrated. Enjoy free technical 
support and rapid, post-paid delivery any- 
where in the Continental USA, JENSEN 
TOOLS INC., 7815 S. 46th St., Phoenix, AZ 
85044. Phone: 602-968-6231; FAX: 
1-800-366-9662. 
CIRCLE 115 ON FREE INFORMATION CARD 






ZF1 



ZF2 



CABLE TV CONVERTERS AND DE- 
SCRAMBLERS SB-3 $79.00 TRI-BI $95.00 
MLD-$79.00 M35B S69.00 DRZ-DIC 
$149.00. Special combos available. We ship 
COD. Quantity discounts. Call for pricing on 
other products. Dealers wanted, FREE CATA- 
LOG. We stand behind our products where 
others fail. One year warranty. ACE PROD- 
UCTS. P.O. Box 582, Saco, ME 04072 1 
(800) 234-0726. 

CIRCLE 75 ON FREE INFORMATION CARD 



ZENITH TEST CHIP (ZF1). New improved 
Data Injector Fully activates Z-tacs $29.95 No 
jumpers to cut. Just solder 4 wires and plug 
chip into socket. ZENITH TEST BOARD 
(ZF2) Fully activates the 165 chip on the 288 
chip's data stream. $49.95 Both units for test 
purposes only, not for signal theft. PHONE: 
800-722-9381 



CALL NOW 
AND 

RESERVE 
YOUR SPACE 



• 6 x rate $940.00 per each insertion. 

• Fast reader service cycle. 

• Short lead time for the placement of 
ads. 

• We typeset and layout the ad at no 
additional charge. 

Call 516-293-3000 to reserve space. Ask 
for Arline Fishman. Limited number of 
pages available. Mail materials to: 
mini-ADS, RADIO-ELECTRONICS, 500- 
B Bi-County Blvd., Farmingdale, NY 
11735. 

FAX: 516-293-3315 




APPLIANCE REPAIR HANDBOOKS— 13 
volumes by service experts; easy-to- 
understand diagrams, illustrations. For major 
appliances (air conditioners, refrigerators, 
washers, dryers, microwaves, etc.), elec. 
housewares, personal-care appliances. 
Basics of solid state, setting up shop, test 
instruments. $2.65 to $7.90 each. Free 
brochure, APPLIANCE SERVICE, P.O. Box 
789, Lombard, IL 60148. (312) 932-9550. 

CIRCLE 84 ON FREE INFORMATION CARD 




SIMPLY SNAP THE WAT-50 MINIATURE FM 
TRANSMITTER on top of a 9v battery and 
hear every sound in an entire house up to 1 
mile away! Adjustable from 70-130 MHZ. Use 
with any FM radio. Complete kit $29.95 + 
$1,50 S + H. Free shipping on 2 or more! COD 
add $4. Call or send VISA, MC, MO. DECO 
INDUSTRIES, Box 607, Bedford Hills, NY 
10507. (914) 232-3878. 

CIRCLE 127 ON FREE INFORMATION CARD 



to 



23 



•rSave on cable rental fees !» 

CABLE TV 

DESCRAMBLERS 

WE'LL BEAT 
ANY PRICE! 

CALL TOLL- FREE 1-800 

284-8432 

JERROLD-TOCOM-ZENITH 
HAMLIN-OAK-PIONEER 
SCIENTIFIC ATLANTIC 

■24 HOUR SHIPMENTS t 
• MONEY BACK GUARANTEE I 
'FREE CATALOG 8, INFO t 
'QUANTITY DISCOUNTS ! 

MASTER CARD / AMEX / VISA / C.O.D. 




Have make and model number of 
equipment used in your area ready 

1-800-284-8432 
CABLE WAREHOUSE 

4700 N. HIATUS R0AD,SUNRISE,FIA33351 
V,, _ NO FLORIDA S^LES >*J 

CIRCLE 180 ON FREE INFORMATION CARD 



Try the 

HectnmtES, 

bulletin board 
system 

(RE-BBS) 
516-293-2283 



The more you use II the 

more useful It becomes. 

We support 300 and 1200 
gaud operation. 

Parameters: SHI (B data 
alts, no parity, 1 stop bit) 
or 7E1 (7 data bits, even 
parity, 1 stop bit). 

Add yourself to our user 
flies to increase your 
access. 

Communicate with other 
R-E readers. 

Leave your comments on 
R-E with the SYSOR 



RE-BBS 

516-293-2283 




A<jiC! 



CO 

o 

z 
o 
ir 

H 
O 



6 
□ 

< 

24 



An ETCHED 

circuit board 

from a 

Printed PAGE 

in just 3 Hours 



The ER-4 PHOTO ETCH KIT gives you the tools, materials and chemicals 
to make your own printed circuit boards. The patented Pos-Neg"* process 
copies artwork from magazines like this one without damaging the page. 
Use the circuit patterns, tapes and drafting film to make your own 1X 
artwork. Or try the Oirect Etch™ system (also included), to make single 
circuit boards without artwork. The ER-4 is stocked by many electronic 
parts distributors, or order direct, postpaid. 

ER-4 PHOTO ETCH KIT (NJ and CA residents add sales tax) S38.00 

DATAK'S COMPLETE CATALOG lists hundreds of printed circuit products 
and art patterns. Also contains dry transfer letter sheets and electronic title 
sets for professional looking control panels. WRITE FOR IT NOW! 
DATAK Corporation • 55 Freeport Blvd, Unit 23 • 
Sparks, NV 89431 

CIRCLE 1B7 ON FREE INFORMATION CARD 



the image to be displayed 
on the screen, adjusted For 
brightness and contrast, 
printed directly to HP 
Laserjet II and compatible 
printers, and saved either 
as linear Files or as TIFF 
Files that can be imported 
to most desktop-publish- 
ing applications. The PFG-1 
also includes a DB9 serial 
cable, a DB9-to-DB25 
adaptor, an RCA video ca- 
ble, and a 9-voit lithium bat- 
tery as well. 

The PFG-1 portable vid- 
eo Frame grabber costs 
$269 —Portable Tech- 
nologies, P.O. Box 
20763, Castro Valley, CA 
94546; Phone: 

415-537-4954. 

RF SIGNAL GENER- 
ATORS. With optional FM- 
stereo-modulation ca- 
pability, the Philips PM 
5327 and PM 5328 RF-sig- 
nal generators From John 
Fluke Mfg. Co. are well 
suited for use in the test 




CIRCLE 19 ON FREE 
INFORMATION CARD 

and repair of consumer au- 
dio electronics. The 180- 
MHz instruments can be 
used either as stand-alone 
benchtop tools or, using 
the GPIB interface, in test 
systems. The PM 5328 
also features a built-in 200- 
MHz frequency counter. 
The signal generators' 
standard modulation 
modes include AM, FM, 
and frequency sweep. A 
high-stability frequency-ref- 
erence option is also avail- 
able to ensure accuracy in 
higher-performance ap- 
plications. Modulation can 
be external as well as inter- 
nal, and parameters such 
as modulation Frequency, 
sweep width, and sweep 
time are user-selectable. 
By providing full, clear in- 



Formation about all signal 
parameters and settings, 
the multifunction backlit 
LCD screen simplifies op- 
eration of the signal gener- 
ators. Push-button-acti- 
vated menus are used for 
setting frequency, output 
level, modulation mode, 
and modulation param- 
eters. The PM 5328 has a 
large rotary-control knob 
with variable resolution, for 
quick selection oF the desir- 
ed value. Frequencies and 
levels can also be set by 
step-by-step adjustments 
or by direct numeric entry 
of the value. 

Both models can store 
and instantly recall com- 
plete front-panel setups. 
The PM 5328 has memory 
for 99 setups and the PM 

5327 can store 10. Stored 
settings can be called up 
remotely, using the GPIB 
interface. Output ampli- 
tude ranges are From -127 
to -7 dBm for the PM 
532 7 and -127 to +13 for 
the PM 5328. 

The PM 5327 and PM 

5328 RF-signal generators 
have base list prices of 
$4900 and $5650, respec- 
tively. The FM-stereo-mod- 
ulation option has a list 
price of $750. — John 
Fluke Mfg. Co., Inc., 
P.O. Box 9090, Everett, 
WA 98206; Phone: 
800-44-FLUKE. 

2-MHz SWEEP/FUNC- 
TION GENERATOR. For 

use in education, produc- 
tion lines, repair shops, and 
hobby or engineering de- 
sign, BelMerit's FG-150 is 
a cost- effective way to ac- 
quire a comprehensive 
sweep/function generator 
with built-in frequency 




CIRCLE 20 ON FREE 
INFORMATION CARD 



counter in one compact 
case. The FG-150 s gener- 
ator section outputs sine, 
square, triangle, ramp, and 
skewed sine waveforms. 
Its frequency is 0.02 Hz to 
2 MHz, and impedance is 
50 ohms ±10%, 600 ohms 
±10%, up to 100 kHz. The 
frequency variable range is 
100:1 and the symmetry 
variable range is 10:1 to 
1:10. The FG-150 has lin- 
ear/logarithmic sweep 
modes. The internal coun- 
ter has 1-Hz, 10-Hz, 100- 
Hz, and 1-kHz resolution: a 
4-digit LED with annun- 
ciators; 100-ms, 1 -second 
gate times, and accuracy 
of time base error plus one 
digit. The external coun- 
ter's frequency range is 1 to 
9999 kHz and its sensitivity 
is 15 mV RMS. 

The FG-150 sweep/ 
function generator with 
built-in frequency counter 
has a suggested list price 
of $295 .— BelMerit 
Corporation, 14775 Car- 



menita Road, Norwalk, CA 
90650; Phone: 

213-802-366; Fax: 
213-802-3298. 

COMPONENT/HDTV 
WAVEFORM MONITOR. 

Designed to provide con- 
venient, precise video-sys- 
tem measurements for 




CIRCLE 2T ON FREE 
INFORMATION CARD 

525/60 and 625/50 com- 
ponent, NTSC and PAL 
composite, and HDTV 
(1125/60) signals. Leader 
Instruments' model 5100 
component/HDTV wave- 
form monitor features four- 
channel output (three 
transcoded to RGB from Y, 
R-Y, and B-Y for 525/60 



systems). Also featured 
are overlaid display of four 
signals, such as Y, R-Y, BY, 
and composite, as well as 
parade displays of three 
channels. A vector display 
of color difference or RGB 
signals checks component 
chrominance, while display 
of the unique "shark-fin" 
signal provides a high-reso- 
lution relative-timing read- 
ing over a wide bandwidth. 
The model 5100 provides 
full raster line selection for 
525/60. 625/60, and 
1125/60 signals. Cursor 
operation makes it easier 
to make level measure- 
ments and to preset mea- 
sured parameters to spec- 
ified values. Powered by 
either 12 VDC or 90-250 
VAC, the instrument is 
completely portable for 
field use. 

The model 5100 compo- 
nent/HDTV waveform 
monitor costs $3800. — 
Leader Instruments 
Corporation, 380 Oser 



Avenue, Hauppauge, NY 
11788; Phone: 

800-645-5104 Cin NY, 
516-231-6900). 

PEN-TYPE DIGITAL 
MULTIMETER. Designed 
for applications where the 
technician doesn't have 
much room to maneuver, 
Beckman s DM73 is a pen- 
style, hand-held digital mul- 
timeter that features a 3'/2- 
digit display with 0.5% ac- 
curacy (DC 2V range) and 
auto-ranging. Its compact 




CIRCLE 22 ON FREE 
INFORMATION CARD 

size, light weight, and sim- 
ple slide switch for chang- 
ing functions make the 
DM73 easy to use for trou- 



PUT THE PC10 EV YOUR PC FOR MORE COUNTER POWER. 



OPTOELECTRONICS does 
it again - phenomenal power, 
performance and price. 

This is what sets our PC Based 
Universal Counter apart from any 
other counter available on the 
market today... 



Model PCI0 Universal Counter 
Timer Board for the PC. 
Introductory Price $339. 

The PC 10 has on board SO ohm RF input 
With antplifiers and prescaiers to operate 
as a stand alone IMHz w 2AGHz RF 
counter. TTL level input signals can he 
connected directly to the miniature 25 pin 
D connector on the mounting bracket. 
For low frequency, high impedance 
inputs, the Model APIOH companion 
amplifier must he used. 
Model APIOH Dual High Impedance 
Amplifier Head L'nd {not sttnwnl. 
Introductory Price S299. 

The APIOH is the companion head unit 
that supports all PC 10 Universal Counter 
functions from 10Hz to 100MHz with 1 megohm 
inputs. Input attenuators, low pass filters and 
trigger levels are software selectable. 
Options; TCXO 1(1 Precision Temperature 
Compensated Time Base $195. 
± 02ppm lO^^O^C. Ippm - year aging. 



• Instant Direct Tune - Set a communications 
receiver such as [COM R7000 to frequency 
detected by counter. Patent pending. 

• Data logging and data file creation to keep 
records or measure frequency drift. 

■ Menu selection for Units includes CPM/RPM. 
Hz, KHz, MHz, GHz, Sec, mS, uS and nS. 

• Software timebase calibration of I ppm TCXO 
timebase. 




• W indows 3 .0 operating env ironment with fully 
developed operating and signal conditioning controls 
accessible through pull down menus. 

In addition to these unique features, PC10 is a 

down right high performance counter— 

• 10 digit 1 0Hz to 2.4GHz frequency range. 

• Measurement Period (Gate Time) continuously 
variable from I milli-second to 28 seconds. 

• Reciprocal Counting for high resolution 
measurement, 

■ Input sensitivity is less than I OrnV from 1 0Hz to 
over 1.6GHz. 

• Direct count frequencies over 200MHz with I Hz 
resolution in 1 sec. 



WW IWl.U.%.1 IW/IVIVJ 

Toll Free Order Line: 1-800-327-5912 
FL(305)771-2050 • FAX(305)771-2052 

5821 NE 14th Avenue • Fort Lauderdale, Florida 33334 




s 

5 



25 



CIRCLE 188 ON FREE INFORMATION CARD 



Get A Complete Course In 

ELECTRONIC 
ENGINEERING 

8 volumes, over 2000 pages, 
including all necessary math and 
physics. 29 examinations to help 
you gauge your personal pro- 
gress. A truly great learning 
experience. 

Prepare now to take advan- 
tage of the growing demand for 
people able to work at the engin- 
eering level. 

Ask for our brochure giving com- 
plete details of content. Use your 
free information card number, or 
write us directly. $59.95 to $119.95, 
Postage Included. Satisfaction 
guaranteed or money refunded. 



~\ 



fV\A/ 



)i 



Banner 
Technical 
Books, Inc. 

1203 Grant Ave. 
Rockford. IL 61103 



Choose From 
Our Line-Up 



CIRCLE 67 ON FREE INFORMATION CARD 




Increase your efficiency and productivity 
wild Tech Spray's complete line of chemi- 
cal products and accessories including: 

Blue Shower" cleaner/degreaser— A last 
and complete contact cleaner safe on 
sensitive components. Contains no CFCs. 

Precision Ouster OF" dusting gas- 
Moist ure-free. zero residue, non-flam- 
mable and non-abrasive. Contains no 
CFCs. 

minus 96 Instant Chiller freeze spray- 
Detects cracks in PCBs, helps prevent 
cold soiderjoirits, protects heat-sensitive 
components and cools components dur- 
ing mounting . Contains no CFCs. 

For more inlormation on these products 

or any other Tech Spray product, contact: 

TechSpray 

P.O. Box 949 • Amariilo, TX 791 05-9935 
800-858-1043 • In TX 800-692-4677 

Fax: 806-372-8750 



CABLE - TV 



SIGNAL RC/HOVCR§ 

•FOR ELIMINATION OF SEVERE INTERFERENCE 
•FOR "CENSORING - OF ADULT BROADCASTS 




-&& 

'^> 



■ ATTENUATION - 45 dB TYPICAL 

■ BANDWIDTH - 4 MHz AT 5 dB POINTS 

■ INSERTION LOSS - 2 dB 



MQQC4 




FOR 
CHANNELS 


PA39UHD 


Pfl.CE 


SH!PPiHO 


J3K 


EC-££ MM.. 


2 3 for 6 ritit' nam| 


SO-300UHI 


MO 


NO 

SHIPPING 

or 

COD. 

CHARGES 


46 FM 


66 10! WHi 


4.5 6 (or any FM} 


50-300 MHz 


130 


1*17 


120.144 MHz 


!4[A)15(BH»[CH7(D] 


50-400 MHz 


t?Q 


1 822 


1 44-1 74 M Hi 


lr)(El 19(F) Z«|G) 21(H) 22 (l| 


50-40C MH: 


J30 


713 


174-216 MHz 


7.1.9.10.11.12.13 


50-400 MH: 


530 



CO 

o 
z 

o 



g 

Q 

< 



3 for $75 - 10 for $200 - mix or match 

CALLTOiLFREEFORCO.D.ORSENDCHECKTOORDER 

FAST DELIVERY 

30 D A Y MON EY BAG K GU AR ANT EE (3 FILTE R L IM IT) 

Star Circuits 

P.O. Box 94917 
Las Vegas, NV 39193-491 7 

1-800-433-6319 



bleshooting and installing 
electronics in tight places 
such as computer boards, 
under a car dashboard, or 
behind an arcade game. 
Another convenience fea- 
ture that comes in handy in 
awkward spots is the data 
hold function, which lets 
the user manually "freeze" 
the display so that it can be 
moved from the measure- 
ment point to take the 
reading. 

Other features of the 
DM73 include an audible 
continuity check, a buzzer 
that sounds when chang- 
ing functions, a built-in 
scabbard for the ground 
probe, and a display of the 
function in use. The DMM 
has full auto-ranging ca- 
pability on 12 measurement 
ranges. DC voltages up to 
500V, AC voltages to 
250V, and resistance up to 
2 megohms are measured 
using an accurate dual- 
slope integrating analog- 
to-digital GVD) conversion 
technique. 

The DM73 pen-type dig- 
ital multimeter, complete 
with batteries, test leads, 
and operator's manual, has 
a list price of $69.95. — 
Beckman Industrial 
Corporation, Instrumen- 
tation Products Division, 
3883 Ruffin Road. San Di- 
ego, CA 92123-1898; 
Phone: 619-495-3200. 

PC-CARD PROTOTYP- 
ING KIT. To provide a 
broad base of PC-users 
with low-cost digital-signal- 
processing (DSP) ca- 
pabilities, Signal-Systems' 
is offering DSPerato, a 
real-time, DSP expansion- 
card prototyping kit that 
features a Motorola 56001 
DSP chip. Motorola's 
56001 DSP runs at 20 
MHz, delivers 10 MIPS, 
and offers advanced tech- 
nologies including pipeline 
instruction fetches; parallel 
data moves to three sepa- 
rate 24-bit CX-data, Y-data, 
and program) memories; 
and easy interfacing to the 



host computer. DSPerato 
contains a full-length IBM- 
PC prototype card that al- 
ready has a bus decode 
and buffer printed circuit. 
The rest of the card has un- 
committed 0.100 center- 
plated through holes with 
power buses and pads. The 
56001 DSP and support 
chips are wired and sol- 
dered on those pads. 

Two optional high-perfor- 
mance video and audio 
A/D and D/A converter 
boards can be attached to 
the card via 0.100 center 
pin headers. The 16-bit au- 
dio board uses Motorola's 
56ADC 16-bit converter; 




CIRCLE 23 ON FREE 
INFORMATION CARD 

the 8-bit video card uses 
Sony's 8-bit 20-MHz semi- 
flash converters. For max- 
imum flexibility in custom 
projects, the user can opt 
for both converters, just 
one, or neither to be at- 
tached to the DSP card. 

Parts needed to popu- 
late the DSP card and the 
converter kits — including 
all chips, sockets, re- 
sistors, and capacitors as 
weli as the 56001 DSP and 
8Kx 24-bit 45-ns static 
RAM — are included. The 
user can add parts as 
needed to configure the 
card for custom applica- 
tions. All assembly instruc- 
tions and schematics re- 
quired for connecting the 
DSP and the converters 
are also included, along 
with Signal-Tools software. 
Signal-Tools' functions in- 
clude real-time spectrum 
analysis , digital os- 
cilloscope, and waveform 
capture and generation. 
The software features a 
keyboard- or mouse-driven 
pull-down menu interface. 



26 



Optionally available is a 
software development kit 
that contains MACRO- 
DSP, a 56001 DSP macro 
assembler for IBM-PC's; a 
debugger, and linkable ob- 
ject modules, 

DSPerato costs $299. 
the audio and video con- 
verter boards cost $149 
each, and the software de- 
velopment kit including 
MACRO-DSP costs 
S99 Signal-Systems 
15105 S.E. East Avenue, 
Mitwaukie, OR 97267. 

800-MHz GROUND- 
PLANE ANTENNA. Be- 
cause broad-band scanner 
antennas perform poorly at 
higher frequencies, many 
scanner listeners hear only 
a small fraction of the sig- 
nals available on the 800- 
MHz band. The MAX800 
800-MHz ground-plane an- 
tenna from Cellular Securi- 
ty Group is a specialized 
mono-band antenna de- 
signed to alleviate that 




CIRCLE 24 ON FREE 
INFORMATION CARD 

problem. Based on plans 
presented in the ARRL 
Handbook, the element 
lengths are cut precisely to 
the proportionate dimen- 
sions. The design supports 
the elements, protects the 
feed-point, and provides a 
quick and easy mounting. 
EMThe MAX800 800-MHz 
ground-plane antenna 
costs $19.95; optional 
type-N connector models 
of long 38-inch PVC 
mounting masts are avail- 
able for an additional 
$ 5 . 00 .—Cellular Security 
Group. 4 Gerring Road, 
Gloucester, MA 01930; 
Phone: 508-281-8892. R-E 



Try the 



Hectm 



miEs r 



bulletin board 
system 

(RE-BBS) 
516-293-2283 



The more you use it the 
more useful II becomes. 

We support 300 and 1200 
baud operation. 

Parameters: 8N1 (8 data 
bits, no parity, 1 slap bit) 
or 7E1 (7 data bits, even 
parity, 1 stop bit). 

Add yourself to our user 
til es to Increase your 
access. 

Communicate with other 
R-E readers. 

Leave your comments on 
R-E with the SYS0P. 



RE-BBS 
516-293-2283 



LEARN VCR 

CLEANING/MAINTENANCE/REPAIR 

EARN UP TO S1000 A WEEK.WORKING 
PART TIME FROM YOUR OWN HOME! 




THE MONEY MAKING OPPORTUNITY 
OF THE 1990S 
IF yen are able to work with common small hand 
tools , and are (ami I iar wi th bas i c electron i cs ( i . e . able 
to use voltmeter, understand DC electronics), . . . 
IF you possess average mechanical ability, and havea 
VCR on which to practice and learn. . . .then we can 
teach 1OT VCR maintenance and repair! 
FACT: u p f o 90% of AL L VCR maltu ratio ns a re d ue to 
simple MECHANICAL or ELECTRO-MECHANICAL 
breakdowns' 

FACT: over 77 million VCRs in use today nationwide! 
Average VCR needs service or repair every 12 to 18 
months! 

Vlejos 400 PAGE TRAINING- MANUAL (over 500 pho- 
tos and illustrations) and AWARD-WINNING VIDEO 
TRAINING TAPE reveals the SECRETS ol VCR mainte- 
nance and repair— "teal world" information that is 
NOT available elsewhere! 

Also includes all the info you'll need regarding the 
BUSINESS-SIDE of running a successful service op- 
eration! FREE ikfoRMATION 

CALL TOLL-FREE 1-800-537-0589 
Or write lo: Viejo Publications Inc. 

5329 Fountain Ave. 
Los Angeles, CA 90029 Dept. RE 



CIRCLE 185 ON FREE INFORMATION CARD 



FREE CATALOG with over 100 innovations 
to add comfort and convenience to your home. 




Latest in electronics. 

Heath Company's new Home 
Automation catalog features easy-to- 
install electronics that bring 
sophisticated technology into your 
home for as little as $12.95. Simple. 
Easy to install. Affordable. 
Guaranteed. 

Some bring you peace of mind. 

Affordable protection for your home or 
car. Expandable security systems to meet 
your needs today and tomorrow. 
Advanced motion sensor lighting that 
reduces false triggering (often caused 
by blowing leaves or small pets) by up 
to 75%, You get protection where 
and when you need it, indoors and 
out. 

Some save you time. 

Watch the kids play outside, 
monitor the baby's room, or 
see who's at the front door 
just by looking at your 
television screen. (Who says 
you can't be two places at once?' 
Call home to turn on your slow-cooker or 
other appliances. From one center, control 
lights, fans, air conditioners — almost 




HOAE 
LHmATION 

B\' HEATH 



anything that plugs into an electrical 
outlet. 

Some just make life easier. 

Add a portable phone extension to any 
electrical outlet. Automatically lower 
the volume of your music system 
whenever the phone rings. Or play a 
movie on the living room VCR and 
watch it on your bedroom 
TV. 

100% satisfaction 
... the Heath 
guarantee for 
over 40 years. 

Try any Heath product at no 
risk. If you aren't completely satisfied, 
simply return the item within six months 
for credit or full refund. 



Call 1 800-44-HEATH for 
your FREE CATALOG. 

Fiee call for a free catalog. Or, just 
mail the coupon below. Heath 
adds comfort and convenience ... 
and makes coming home even 
better. 

Heath 

Benton Harbor, Michigan 



W. 



Please send me the 
NEW Home Automation 
catalog. 

Name 



Address 



Apt. 



Cily_ 



State 



Zip. 



Mail to Heath Company, Dept. 020-050, 
Benton Harbor, MI 49022. 

II A- 101 I 



S 
S 

1 



27 



CIRCLE 86 ON FREE INFORMATION CARD 






NEW LIT 



Use The Free Information Card for fast response. 



w 
o 

2 

o 

□r. 

h- 
o 

LU 
_J 
UJ 

6 

Q 

< 



HDTV: HIGH-DEFINI- 
TION TELEVISION; by 
Stan Prentiss. Pub- 
lished by Tab Books 
Inc., Blue Ridge Summit, 
PA 17294-0850; Phone: 
1-800-233-1128; $16.95. 

Already a reality in Japan 
(albeit with a steep price 
tag and limited program- 
ming), HDTV is eagerly 
awaited around the rest of 




CIRCLE 37 ON FREE 
INFORMATION CARD 

the world. More than a doz- 
en major corporations cur- 
rently are competing to 
perfect the revolutionary 
technology that promises 
to bring crystal-clear pic- 
tures and high-quality 
sound to television. This 
book is intended to help 
prepare engineers, techni- 
cians, students, and mar- 
keting managers for the 
unveiling of HDTV. 

The book provides an in- 
side look at both the tech- 
nical and the legislative 
aspects of high-definition 
television. It explores the 
widely divergent industry 
standards in North Amer- 
ica, Europe, and Japan that 
are now impeding HDTV 
production, and analyzes 
FCC and congressional 
regulation of HDTV re- 
search and development in 



the U.S. The book explains 
the competing delivery and 
receiving systems under 
development, discussing 
their pros and cons and de- 
scribing the methods used 
to create those systems. In 
addition, the book covers 
the progress of HDTV vari- 
ants that could enhance 
the performance of stan- 
dard TV receivers, such as 
improved-definition televi- 
sion and extended-defini- 
tion television. 

HEATHKIT WINTER 1991 
CATALOG. From Heath 
Company, Department 
350-054, Benton Harbor, 
Ml 49022; Phone: 
1-800-44-HEATH; free. 

Bound into this 60-page 
catalog is a special "Home 
Automation" insert that de- 
votes 28 pages to a variety 
of innovative products for 
safety, security, con- 
venience, entertainment, 
and energy management in 
and around the home. 
Aimed at do-it-yourselfers, 




CIRCLE 38 ON FREE 
INFORMATION CARD 

the home-automation prod- 
ucts include whole-house 
automation and security 
systems, motion-sensing 
indoor and outdoor lights, 
wall switches, wireless vid- 
eo broadcasters, wireless 
phone extensions, flood 
sensor alarms, an elec- 



tronically controlled pet 
door, and automatic-lawn 
sprinkling systems. The 
main catalog includes a va- 
riety of easy-to-build elec- 
tronic kits as well as tools, 
weather instruments, com- 
puters, amateur-radio 
equipment, home-enter- 
tainment products, and 
home-study electronics 
courses and videos. 

CONSUMER ELEC- 
TRONICS SYSTEMS 
TECHNICIAN SAFETY 
GUIDELINES. From EIA/ 
CEG, Department PS, 
2001 Pennsylvania Ave- 
nue, N.W.. Washington, 
DC 2006-1813; $1.00. 

Although manufacturers 
strive to make their prod- 
ucts safe to use and to ser- 
vice, and student techni- 
cians are taught the inher- 
ent dangers in the work, 
technicians often tend to 
become complacent with 
experience. This brochure 
is intended to remind them 
of possible dangers and to 
keep safety considerations 
a conscious part of their 
work, it contains important 
safety guidelines that 
should be followed and up- 
dated UL requirements for 
safe installation and servic- 



CONSUMEH ELECTHONICS 
SYSTEMS TECHNICIAN 
SAFETY GITTDEI.TNK5 



SAFETY 
SAFETY 
SAFETY 
SAFETY 
3 FETt 
SAFETY 
SAFETY 

sflFFTY 



GUIDELINES 
GUIDELINES 
GUIDELINES 
GUIDELINES 
GUIDELINES 
GUIDELINES 
GUIDELINES 
ninnFT.TWFP 



ing of antennas, TV's, and 
other consumer-elec- 
tronics products. 

U.S. GOVERNMENT 
BOOKS FOR BUSINESS 
PROFESSIONALS. 
From U.S. Government 
Printing Office, Free 
Business Books Cata- 
log, Stop SM, Wash- 
ington, DC 20401 ; free. 




EXPOB17 IMPORT ._ 

mum t tudbumu. 
*ccomrrtNc haxes 

LAW . 

Ldur Bdilfeu, Uwi & SUUtiJa 
Selltajf m ihc Gumiir: 



— i 




CIRCLE 39 ON FREE 
INFORMATION CARD 



CIRCLE 40 ON FREE 
INFORMATION CARD 

Whether you own your 
own company, have joined 
the ranks of those who are 
supplementing their day 
jobs by running a second 
business from their homes, 
or come up with patentable 
creations on your work- 
bench, the publications 
listed in this catalog con- 
tain information you'll find 
valuable. Intended to 
create greater awareness 
of and access to govern- 
ment information for the 
business community, the 
22-page catalog contains 
the most popular govern- 
ment business books and 
subscriptions that are sold 
to the public. Those pub- 
lications cover such fields 
as accounting and taxation, 
selling to the government, 
exporting, labor law, pat- 
ents and trademarks, and 
business statistics, R-E 



28 



CIE Gives You The Training You Need to Succeed, 
At Your Own Pace... & In Your Own Home! 

Discover Your Career Potential In The 
Fast-Growing Field Of High-Tech Electronics! 



If you're anxious to get ahead ...and 
build a real career... you owe it to 
yourself to find out about the Cleveland 
Institute of Electronics! 

CIE can help you discover your 
career potential in the fast growing 
field of high-tech electronics. A career 
that will challenge and excite you 
every day... re ward you with a powerful 
feeling of personal accomplishment... 
and deliver a level of financial security 
you may have only dreamed of before! 

As the leading school in home-study 
electronics, CIE has helped over 
150,000 students in the U.S.A. and 
over 70 foreign countries get started in 
this exciting field. To find out how CIE 
could be helping you... read on... then 
send for a CIE catalog TODAY! 

A Growing Need For 
Trained Professionals! 

The career opportunities shown here 
are only a few of the challenging, high- 
paying careers you could enjoy as an 
electronics technician. 

You could be the "brains" behind the 
scenes of an exciting TV broadcast... 
trouble-shoot life-saving medical equip- 
ment... design exotic new aeronautics 
systems... C I Es job-oriented programs 
offer you the quickest possible path to 
the career of your dreams! And CIE also features 
military and union re-training, to build on what 
you already know. 

Dozens Of Fascinating 
Careers To Choose From! 

Even if you aren't sure which career is best for 
you, CIE can get you started with core lessons 
applicable to all areas of electronics. As you 
advance, CIE makes job opportunities available 
to you through the bimonthly school paper, 
The Electron. 




Consumer Electronics 



Military Electronics 



Personal Training From A 
Renowned Faculty. 

Unlike the impersonal approach of large class- 
room study, CIE offers you one-on-one instructional 
help 6 days a week, toll-free. Each CIE lesson is 
authored by an independent specialist, backed by 
CIE instructors who work directly with you to 
answer your questions and provide technical assis- 

.„„ tance when you need it. 

+^ * ^ 



Practical Training... 
At Your Own Pace. 

Through CIE, you can train for your 
new career while you keep your pres- 
ent job. Each course allows a gener- 
ous completion time, and there are 
no limitations on how fast you can 
study. Should you already have some 
electronics experience, CIE offers 
several courses which start at the 
intermediate level. 

"State-Of-The-ArT 
Facilities & Equipment. 

In 1969. CIE pioneered the first elec- 
tronics laboratory course, and in 1 984, 
the first Microprocessor Laboratory. 
Today, no other home study school can 
match CIEs state-of-the-art equipment. 
And all your laboratory equipment is 
included in your tuition cost. There is 
no extra charge— it's yours to use while 
you study at home and on the job after 
you complete your course! 

Earn Your Degree To 

Become A Professional 

In Electronics! 

Every CIE course you take earns you 
credit towards the completion of your 
Associate in Applied Science Degree, so 
you can work towards your degree in 
stages. And CIE is the only school that awards you 
for fast study, which can save you thousands of 
dollars in obtaining the same electronics education 
found in four-year Bachelor's Degree programs! 



Send For Your 
Catalog Today! 



r jf 






CIE World Headquarters 




■& 



S 



€ '«*• 



J5* 






// 



/o *E S-f^ 



7/f 







Cleveland Institute of Electronics, Inc. 
1776 East 17th St., Cleveland, Ohio 44114 

□ YES! Please send me your independent study catalog (For your convenience, 
CIE will have a representative contact you— (tee is no obligation.) 



Apt* 



Area Code/Phone Nq 



Check to tor G.I. Bill bulletin on educational benefits: o Veteran □ Active Duty 



Mail This Coupon Today! 



AE10 



to 

CO 



31 




PARTS SPECIAL-ORDER HOTLINE. Your local Radio Shack offers a Huge 
selection of electronic components. Plus, we can special -order over 10,000 
items from our warehouse — ICs. tubes, semiconductors, crystals, phono car- 
tridges and styli, even SAMS* manuals. Delivery time for most items is one 
week. And there are no postage charges or minimum order requirements. 



BATTERY SPECIAL-ORDER HOTLINE. In addition to our large in-store stock, 
Radio Shack can now supply almost any currently manufactured consumer- 
type battery — quality replacements for cordless telephones, computer mem- 
ory, camcorders, transceivers, pagers and more. Discover the Radio Shack 
"hotline" advantage— fast service with no postage or handling charges. 




I 



<1) High-Speed 12VDC Motor. Up 
to 15.200 RPM. About 2" long (with 

shaft). #273-255 2.99 

(2) Ho bby M otor. For robotics a n d 
projects. 1Va to 3VDC. About 1</z" 
long. #273-223 99« 



Heavy-Duty Plug -In DPDT Re- 
lays. Contacts rated 10 amps at 
125 VAC. Size: 1=fex 1 x W. 

12VDC Coil. #275-216 5.99 

125VAC Coll. #275-217 5.99 

Relay Socket. #275-220 ... 1 .79 



(1) Mini Plezo Speaker. Only 
Whz" diameter. #273-091 . . 2.49 

(2) "Ding-Dong" Chime. Re- 
quires 6 to 18VDC. #273-071 . . B.99 

(3) Mini Buzzer. Loud, yet only 7 
mA at 12VDC. #273-074 . . . 2.99 



DPDT Knife Switch. Just the thing 
for low-power switching in science 
projects, model railroads and 
more. Rated 0.5 amp at 200VDC. 
Screw terminals. Mounting holes 
on base, #275-1537 1.29 



Lamp Holders. 
For indicators and 
projects. Figs. 1 
and 2 accept £-10 
threaded-base 
bulbs, available at 
Radio Shack. 



(1) Round Style. 
Screw terminals. 
#272-357 .796 
(21 Compact. 
Solder lugs. 
#272-356 . . 99 C 

(3) Bayonet Base. 
#272-355 . . B/9BC 



O 

Z 

o 

□c 

r- 
o 

LU 

-I 

LJ 

6 
a 
< 



32 



XLR Connector; 

(1) Inline Socket. 
hZTA-mi 2.99 

(2) Three-Pin Plug. 
*274-010 2.99 

(3) Panel Socket. 
#274-013 3.69 

(4) Adapter Trans- 
former. Connects 
XLR-type mike to 
equipment wilh U*" 
phone jack input. 
#274-016 . . . 11.99 

(5) Adapter Trans- 
former. Connects 
mike with V>T plug 
to XLR jack input. 
#274-017 . . 11.99 




M (S) 



LCD DVM With 
Capacitance 
and Transistor 
Gain Ranges. 
Extra-feature 
digital multitester 
with easy-to- 
read 0.5" display 
and 10 megohm 
input. 30 ranges- 
measures AC/DC 
voltage and cur- 
rent, resistance, 
capacitance and 
transistor gain. 
#22-194 . . 79.95 



(11 Precision Ther- 
mistor. Resistance 
changes in proper. 
lion to temperature. 
Has measurement 
range Irom -50 lo 
+ 110° c, 
#271-110 .... 1.99 

(2) Surface-Mount 
Resistors. Big 200- 
piece assortment' 
Popular values, 
rated 'fc wan, 5%. 
#271-313. Set 4.9S 

(3) Ohm's Law 
Guide. Fast an- 
swers lo Ohm's law 
and parallel resist- 
ance problems. 
#271-1211 . ...49e 



(1) Telescoping 
Antenna. Ex- 
tends to 24". (16 
styles in stock.) 
#270-1413, 3.99 

(2) "N" Battery 
Holder. (14 other 
styles in stock.) 
#270-405 . . 59e 

(3) Mlnl-Hook 
Adapters, Slip on 
test probe tips. 
#270-334, Pr./2.59 

(4) Micro-Hook 
Test Clips. 
#270-355 ..2.69 



(1) Prewired Tem- 
perature Module. 

Just add one "AA" 
battery for use as a 
Ihermomeler. You 
can also connect 
simple circuits 10 
control external indi- 
cators and devices 
at temperatures you 
set. (Data included.) 
Has 'fe* liquid crys- 
tal display and 
selectable Fahren- 
heit or Centigrade 
modes Module is 
easily panel- 

mounted. 
#277-123 ...19.95 




© 



1 '?5.*?c 



<i> 



n" 



!■ 



Since 1921 Radio Shack has been the place to obtain up-to-date 
electronic parts as well as quality tools, test equipment and accessories 
at low prices. Over 7000 locations to serve you— NOBODY COMPARES 

Prices apply al participating Radio Stuck stores and dealers. Radio Shack is a division oi Tandy Corporation 

CIRCLE 78 ON FREE INFORMATION CARD 



Portable Short- 
wave Antenna. 

Dramatically im- 
proves reception 
on worldband 
portables! Con- 
nector clips to tel- 
escoping rod an- 
tenna. Antenna 
wire extends up 
to 23 feet— and 
winds up on 
pocket-size reel 
for convenient 
storage, travel. 

#278-1374, 8.95 



(2) Set of 100 Ce- 
ramic Disc Capaci- 
tors. A variety of 
popular styles and 
values at a bargain 
price. Ratings up to 
1000 WVDC. Stock 
upl 
1272-801, Set 1.98 



(3) Assortment of 
20 Electrolytic Ca- 
pacitors. Miniature 
and s u bm mi types i n 
a variety ot values 
wilh ratings 10 50 
WVDC. 
#272.802, Set ot 2fjf 1.96 



.Radio /hack 

AMERICA'S TECHNOLOGY 




FRED HUFFT 



EOR EXPERIMENT 

,nal-computer h 
you have probabl 
of memory cj 

access memory I or "DRAM" (dy- 
namic RAM). When troubleshoot- 
ing a PC memory problem, 
expanding RAM capacity? or up" 
grading the cycle speed pi' a mpm 
ory bank, it can be very helpful lo 
have a way of function testing 
and measuring the access tin1e 
or speed of tfieMiRAM IC's. ManJ 
intermittent memory failures 
have been traced to a si' 
in the memory bank 
other hand, some DRAMs will far 
exceed their minimum access 
rating and can be speed tested 
and sorted for faster functions, 
saving the cost difference to the 
faster rated parts.' 

A number of small DRAM test- 
ers are available from ^bout $150 
to $1000, with the less-expensive 
models not having Jk lot . of fea- 
tures. However, if you are inter- 
ested in buildjTjg a' multi- 
featured unit that can function 
test, accurately speeds 'test, and 
automatically cycle the 1 tests un- 
der high-, low-, or normal-voltage 
margins, all for less than $60" - 
(plus enclosure and AC adaptor), 
then check out this easy-to-as — 
semble DRAM Tester. 

Capabilities 

The unit can test 64Kxl. 
256KX1, or lMEGxl DRAM's, , 
and can measure speed or access * 
times from 60 to 200 nanosee 
conds (ns). There is a switch, "fo 
select a "HI" and "LO" voltage- / 
margin test and three LED in-' 
dilators that show the current 
deviee-under-test (DUT) voltage. 
There's also a red/green LED that 
blinks green to show a test is run- 
ning, displays a continuous 
green to show a test has run com- 
plete without an error, and will 
display a continuous red when a 
test is stopped by the detection of 
an error. 

An 18-pin Z1F (zero insertion 
force) test socket is provided for 



'uiid a sophisticated DRAM tester witfy 
functi on-s peed, and margin test. 
for under $60! 




vm 





^*° 



****r 



-*v^ 




'l-MEG DRAM's l 
test socket is us_ 
and 256g DRAM's. A pushbutton 
test switeh"starts a test se^ 
quence. which runs about, 10' Lo 
14 seconds depending on th"5 ac* 
cess speed. However, a cycle 
switch is provided to continu- 
ously recycle the selected test, if 
desired. When a 1-MEG DRAM is 
tested, a 0101 data pattern is 
written to all addresses in the 
DRAM, then each address is read 
back and compared for correct 



in ZIF data. An error stQp* will occur fnrr- 



the data is not correct. 

After the 0101 pattern test, a 
1010 pattern is written to all loca- 
tions, then read back and com- 
■ pared. The two-pattern test is 
automatically run twice: upon 
successful completion of the two- 
pattern double test, the tester 
stops and indicates a continuous 
green on the pass/fail indicator. 

A 256K DRAM receives the 
same test except that it's written 



to 
o 

z 

o 

F- 
O 

UJ 



g 

Q 

< 

r£ 



to and read back 4 times during 
each test and a 64K DRAM re- 
ceives the write/read test 16 times 
in each pattern. If the cycle 
switch is on, the test does not 
stop and will continue until an 
error is detected. If the margin 
switch is on, the first two-pattern 
test cycle will be run at low-mar- 
gin DUT operating voltage and 
the second cycle will automat- 
ically switch to high-margin DUT 
operating voltage. Should both 
the margin and cycle switches be 
on, the tests will alternate from 
low- to high-margin voltage. All 
voltage and test signals are ap- 
plied to both ZIF test sockets si- 
multaneously, but only one 
DRAM can be tested at a time. 
DRAM s to be tested can safely be 
inserted or removed from the ZIF 
test sockets with the power on. 

Dynamic RAM 

DRAM's use multiplexed row 
and column address inputs; 64K 
DRAM's require only 7 address 
lines. 256K DRAM's require 9, 
and 1-MEG DRAM's require 10. 
Figure 1 shows a block diagram 
of a typical 256K x 1 DRAM, and 
Fig. 2 shows a typical 1-MEG 
DRAM. Address decoding and ad- 
dress latches are incorporated in 
the DRAM. To address the DRAM, 
row-address data is put on all ad- 
dress lines and clocked by the ras 
(row address strobe) signal, then 
the column address data is put 
on the address lines and clocked 
by the cas (column address 
strobe) signal. DRAM's have a 
read/write input pin, usually la- 
beled w, to control the type of op- 
eration; a data in pin, d; and a 

DATA OUT pin, Q. 

Data is held in dynamic RAM 
by the charge on internal capaci- 
tors. Since the charge degrades 
with time, the bits need to be "re- 
freshed" or row addressed at ap- 
proximately every 4 to 64 millise- 
conds. That is typically done by a 
RAS-only cycle through the row 
addresses — a normal read or 
write cycle will also accomplish 
the refresh. A 1-MEG DRAM may 
have a "test function" input (tf) 
at pin 4 that allows it to be tested 
4 bits at a time; we do not use 
that function so the tf input is 
disabled by tying it to ground. 

The timing of the address and 
strobe inputs is critical. A 
DRAM's "access time," or speed, 
is the time from ras, which is the 




PIN ASSIGNMENT 

1L 

15- 
11 
13- 
12. 
1L 

10. 

i_ 



1 

2 
3 
A 
5 
6 
J_ 


Afl 


Vss 


D 


CAS 


W 


Q 


RAS 


A6 


AO 


A3 


A2 


A4 


A1 


AR 


- A 


Vcc 


A7 



PIN NAMES 

A0-A8 ADDRESS INPUT 

D DATA IN 

Q- DATA OUT 

W" -READ/WRITE INPUT 

RAS - • ■ ■ ROW ADDRESS STROBE 

CAS COLUMN ADDRESS STROBE 

Vjc- POWER (+5V) 

V ss GROUND 






W- 



3D- 



CAS- 



N0. 2 CLOCK 
GENERATOR 



A0- 
A1- 
A2- 
A3- 
AH- 
A5- 
A6- 
A7- 
A8- 



RAS- 



— N 
-yl 



COLUMN 

ADDRESS 

BUFFERS (9) 



REFRESH 
CONTROLLER/ 
COUNTER (8} 



ROW ADDRESS 
BUFFERS (9) 



NO. 1 CLOCK 
GENERATOR 



DATA IN 
BUFFER 



DATA OUT 
BUFFER 



COLUMN 
DECODER 




5 S 
oo 



1024 



SENSE AMP 
I/O GATING 



"25d 



fH 



1024 



r 



MEMORY 
ARRAY 



^33 



FIG. 1— 256K DRAM PIN NAMES AND BLOCK DIAGRAM. DRAM's use multiplexed row 
and column address inputs; this 256K DRAM requires 9. 



TABLE 1 





Parameter 


'rc 


Random Read or Write Cycle Time 


Wc 


Access Time from RAS 


*CAC 


Access Time from CAS 


Wf 


Output Buffer and Turn-Off Delay 


w 


RAS Precharge Time 


'ras 


RAS Pulse Width 


*CAS 


CAS Pulse Width 


'rcd 


RAS to CAS Delay Time 


*A5R 


Row Address Setup Time 


'rah 


Row Address Hold Time 


Use 


Column Address Setup Time 


*CAH 


Column Address Hold Time 


'afi 


Column Address Hold Time Referenced to RAS 


l RCS 


Read Command Setup Time 



start of the addressing, to the 
time at which there is valid data 
at the output pin d. That is very 
basically how the DRAM works. 
Figure 3 shows a read-cycle tim- 
ing chart for a 256K x I DRAM, 
and Table 1 explains what the 
timing symbols mean. 



Circuit description 

The DRAM tester uses two volt- 
age-regulator IC's and only six 
logic IC's, thanks to the use of two 
PLD's (programmable logic de- 
vices) which replace about ten in- 
dividual IC's. Refer to the block 
diagram in Fig. 4 and the sche- 



34 




D 


Vss 


W 
RAS 



CAS 


TF 


A9 


AO 


A8 


A1 


A7 


A2 


AG 


A3 


A5 


Yoc 


A4 



PI N NAMES 

A0-A9 ADDRESS INPUT 

D DATA INPUT 

Q_- DATA OUTPUT 

W- READ/WRITE ENABLE 

RA& ROW ADDRESS STROBE 

CAS COLUMN ADDRESS STROBE 

V cc POWER (+5V) 

V SE GROUND 

TF -TEST FUNCTION ENABLE 

MC NO CONNECTION 




FIG. 2—1 MEG DRAM PIN NAMES AND BLOCK DIAGRAM. Address decoding and address 
latches are incorporated in the DRAM. 




x: 



"RoW 

ADDRESS 



mJkZA 



te; 



'•sea — ^j 



"k«H" 



^AH 



/ 



Z7 



SCGffiSKSm 



'«c- 



(DATA OUT) ]J<'> , > 



-KIGHZ- 



"TOd" 
DATA 



:> 



FIG. 3— DRAM READ CYCLE AND TIMING Dl AG R AM f or a 256K x 1 DRAM. Table 1 explains 
what the timing symbols mean. 



matic in Fig. 5. An AC power 
adaptor supplies 9 volts DC at 
150 mA to a full-wave bridge rec- 
tifier made up of D5-D8, which 
provide automatic input-polarity 
protection. The 5-volt regulator, 
IC7, supplies power to everything 
but the DUT (device under test). 
DUT power is supplied by IC8, an 
LM317LZ adjustable regulator 
which is controlled by logic in the 
PLD, IC5. For a normal test, IC8 
outputs 5 volts to the DUT. Other- 
wise, 4.5 volts is supplied for the 
low-margin test and 5.6 volts for 
the high-margin test. 

As mentioned before, IC5 and 
IC6 are TTL PAL devices; IC5 is 
an MM1/AMD PALI6L8B-2CN 
low-power, 25-ns device that con- 
tains the oscillator circuitry for 
our system clock. Components 
R15, R16, C12, and C5 are also 
part of the oscillator. The addi- 
tional components R14, R5 (the 
access-time potentiometer), R19 
(the calibration trimmer), and 
R17 (the dial-spread trimmer) 
form the speed-test circuit which 
varies the basic system clock. 

The clock output at IC5 pin 15 
is fed into IC6 pins 1 and 6. When 
the start test switch SI is 
pressed, a start/reset signal is 
generated through R7, C2, and 
R8 which resets 1C2 and IC3 at 
pin 11; the signal is also applied 
as an input to IC6 pin 8. Logic in 
IC6 will gate an output clock sig- 
nal, designated clki, at pin 14, 
That drives pin 10 of IC2 which is 
part of a 24-stage ripple-carry 
binary counter consisting of two 
74HCT4040S (IC2 and IC3). As 
the clock increments the IC2/1C3 
ripple counter, the Q0-Q7 and 
Q10-Q17 outputs drive 1C1 and 
1C4, which are 74HCT257 quad 
2-input multiplexers. 

Multiplexers IC1 and IC4 each 
select four bits of data from two 
different sources under the con- 
trol of a common select input at 
pin 1. Logic in 1C6 generates the 
ras signal which is input at pin 3 
of IC5, present at pin 3 of test- 
socket ZIF1 and pin 4 of Z1F2, 
and is also the input select signal 
at pin 1 of IC1 and IC4. The out- 
puts of 1C1 drive address lines 
A0-A3 and the outputs of IC2 
drive A4-A7 of the DUT at test 
sockets ZIF1 and ZIF2. A 256K 
DRAM requires an additional ad- 
dress line, A8, and a 1-MEG 
DRAM requires two additional 
address lines, A8 and A9. To gen- 



to 



35 



erate the A8 and A9 address 
lines, Q8. Q9, Q18, and 9 19 from 



IC2 and IC3 are logic inputs to 
IC6 which generates the A8 out- 




RG. 4— DRAM TESTER BLOCK DIAGRAM. The DRAM tester uses only six logic IC's, 
thanks to the use of two PLD's. 



put at pin 19 and the A9 output at 
pin 12. 

Both PALs (the 16R4 and the 
16L8) are rated at 25-ns internal 
gate propagation delay. That de- 
lay is an integral part of the sys- 
tem timing, and is used to 
determine the timing of the low 
cas signal at pin 12 of IC5 about 
40 ns after ras goes low. The cas 
signal is applied to the DUT 
which gates the column-address 
data after the row-address data 
has been gated. At the intersec- 
tion of the row address and col- 
umn address, we have the 
selected bit location. Output Q20 
(IC3 pin 12) from the 24 -stage 
ripple counter will determine if 
the operation will be a write or 
read cycle in the DRAM. 

From the start of the test, Q20 
applies a low to the DUT read/ 
write inputs at ZIF1 pin 2 and 
ZIF2 pin 3. The low signal puts 
the DRAM in the write mode for 
the first half of the test, where we 
cycle through all of the address 
locations. Note that, as the ripple 
counter gets to Q20, we have cy- 
cled through all address loca- 
tions in a 1-MEG DRAM once. 



J 



|» » /» * s -%=^\ * r> ^ * *"- » * 



g i— rS — s , / ^ |-j 

■ ;t5=Si I ' ' * 

* — ^c— -&=?— r 71..» - 



if) 
O 

Z 

o 
cc 



o -| 

ill , 



Jm. j /^j^m m top - side a I *l - ^^^^_ 




1*1* "t, "■ • B lv"J ^ B hJ> n fbi 

L_r*5T *: # v •■uF-ru 



■3.35IHCHES- 



-*\ \- 



r 



■3,35 INCHES - 



■*J 



§ TOP, OR COMPONENT SIDE of the DRAM tester PC board. Parts BOTTOM, OR SOLDER SIDE of the board. 
cc are actually mounted on both sides of the board. 

36 



< 3 s. -n 
SB - o 

3- g — 3] 
(D C 3" j, 

JTJ ffl 2 

i5' £. D H 

(O = ? 33 
J7° -? 

bit 2 

-3 9 

»i _, 

tn — 3 

< 3 * 



—1— 2?0tl 



SI 
START TEST 



TDK = " 



Jl 
POWIH 



9" 



»g£ 
<*> ' 2 
c » ,S 

"O 3 <2 

Q. w° 

-* t~ o 
<& fla oq 

T w — 

3 £S" 
b 2 w 

(3 » T3 
III 

-* i o 
^> 00 1 



us 

mil' 
-M- 



W IB 

lKtOW INWH 

— w — t — ** — 



|J-|V,|, 7I0S Van Jit. 

am 



c.i 
.Iiif 



tP-Ov 



ipio S? 



1CS 
v LKS17L v oot 

— V 



FM0 . ; 
22HG : ■ 




u—> 



m 

2?0it 



STUBT.flEBET 



D 00 

12 11 10 09 oa 0? 06 ib 04 03 02 Ql 



C4 
lOftlf 



^ 



Q Q 

12 11 10 OS 08 07 06 05 Ql 03. 0! 01 



012 



013 



Mil 



ms 



a«. 



_H!Z_ 



• ■..-.v-.-i 



_0JL 



..fl'a 



VL 



tunem 



-a^ 



CYCLE 

(OPFN.Ofl) 



OWfJUWHSEl) 



>I0K 



(sroi»)aa 



, -1 



MARGIN 



fcidmBMBBEgT 



HI 2 

IK 



R13 
B1U) 



C12 

ILu' 




L66I- AVW 



w 
o 

z 
o 

IT 

F 

o 

hi 



D 
< 



four times in a 256K DRAM, and 
sixteen times in a 64K DRAM. 
The Q20 output is also input to 
pin 6 of IC5, which will generate a 
d, n signal, which will determine 
the data bit (high = 1 , low = 0) ap- 
plied to the DUT at ZIF1 pin 1 and 
ZIF2 pin 2. Signals Q0 and Q21 
are also applied to IC5 at pins 1 
and 7 respectively; Q0 is used to 
alternate the bit pattern at every 
other location as it is triggered 
every cycle or clock time, and Q21 
is used to change the pattern 
from 010101 to 101010 during the 
second write cycle. Every DRAM 
location will have both a 1 and a 
written to it and read back 1 to 16 
times per test, depending on the 
type of DRAM. 

During the read cycle, the ac- 
cess time of the DRAM is the time 
between the ras and D oirr (valid 
data out) signals, or the time 
from the first address strobe un- 
til valid data is at the q output of 
the DUT. The q output is a three- 
state signal that switches to a 
high-impedance mid-logic level 
when the gas signal goes inac- 
tive. As each address is cycled 
through during the read portion 
of the test, the data bit read out is 
applied to pin 1 1 of IC5 and com- 
pared with the expected bit. If the 
data does not match, an error 
signal is generated at pin 19 of 
IC5 that goes to pin 9 of IC6 
where the fail output will go high 
and the clki output will stop. 
That will halt the ripple counter 
and make pass/fail indicator 
LED4 light a continuous red. 
(LED4 should have been blinking 
green during the test.) 

The margin switch S2 is "on" 
when the contacts are open — 
that removes the ground from 
pin 5 of IC5, allowing pull-up re- 
sistor R4 to switch the input 
high. The logic in IC5 will then 
switch the low output from pin 
17, which selected a normal DUT 
operating voltage of 5.0V, to pin 
16, which selects a low-margin 
voltage of 4.5V. Indicators LED1, 
LED2, and LED3 show which 
DUT operating voltage is cur- 
rently selected, and will remain 
illuminated after an error stop to 
indicate what operating voltage 
was selected at the time of failure. 
The Q22 input at pin 8 of IC5 will 
switch the low-margin test to 
high, and select the pin- 18 out- 
put of IC5, which lights LED3 to 
indicate a high- margin operating 



voltage of 5.6V 

The IC5 outputs that select the 
appropriate LED indicator also 
directly control the DUT voltage 
by applying a ground to R12 via 
pin 17, R13 via pin 16, or neither 
when pin 18 (high margin) is se- 
lected. That affects the adjust- 
ment pin regulator IC8 which 
produces V DUT . 

The cycle switch S3 is "on" 
when the contacts are open, al- 
lowing the pull-down resistor R3 
to hold pin 7 of IC6 low. The high- 
est bit in our ripple counter, Q23, 
is the stop bit. When Q23 goes 
high, the two-pattern test has 
run twice. Switch S3 simply pre- 
vents the high Q23 output from 
reaching the logic input of 1C6. If 
you prefer cycling the two-pat- 
tern test once and stopping in- 
stead of twice, simply disconnect 
Q23 from S3 and connect Q22. 
However, if that is done, the mar- 
gin test would have to be run 



with the cycle switch also "on" 
so that the high-margin test is 
run. With actual usage, it is con- 
venient to use the cycle switch 
most of the time. Just increase 
the access time until the DRAM 
fails, then decrease the speed 
slightly and restart the test to 
quickly determine the speed of 
the part. 

Capacitors CI, C3, C6, and 
C8— Cll are for power bypass, 
and Rl is used to limit the cur- 
rent flow through LED4. Resistor 
R2 limits the current through 
LED1, LED2, and LED3, which 
are discrete red LED's. 

Using PAL's 

The programmable array logic 
device, known as a PAL, was in- 
vented about 15 years ago at a 
company called Monolithic Mem- 
ories, which is now part of AMD 
(Advanced Micro Devices). The 
PAL provides a way of combining 



PARTS LIST 


All resistors are Vi-watt, 5%, un- 


Other components 


less otherwise noted. 


SI — normally-open pushbutton 


Rl— 91 ohms 


switch 


R2— 330 ohms 


S2, S3— SPDT sub-mini slide switch 


R3, R4, R8, R14-R16— 10,000 ohms 


J1 — 2.1 mm DC power input jack 


R5— 1000 ohms, linear taper 


ZIF1— 18-pin ZIF socket 


potentiometer 


ZIF2— 16-pin ZIF socket 


R6, R18— not used 


Miscellaneous: PC board, four 16- 


R7, R9, R1 0—220 ohms, 1% 


pin IC sockets, two 20-pin IC sock- 


R11— 560 ohms 


ets, knob for R5, cabinet, 120- VAC- 


R12— 2000 ohms, 1% 


to-9-VDC 300-mA wall adapter, 


R13— 910 ohms 


solder, etc. 


R17 — 5000 ohms, 4-turn trimmer 


Note: The following items are 


potentiometer 


available from Startek Interna- 


R19— 2000 ohms, trimmer 


tional Inc., 398 NE 38th St., Ft. 


potentiometer 


Lauderdale, FL 33334. For infor- 


Capacitors 


mation call (305) 561-2211, for or- 


CI, C3, C6, C8-C11, C14— 0.1 \sJF, 


ders call (800) 638-8050, FAX 


monolithic 


(305) 561-9133. 


C2 — 1 ^F, tantalum 


• Complete DRAM tester kit in- 


C4, C7— 100 n.F, electrolytic 


cluding programed PAL's (does 


C5, C12— 15 pF, monolithic 


not include cabinet and AC 


Semiconductors 


adaptor), KIT #DT-90K— $59.95. 


IC1, IC4— 74HCT257 quad 2-chan- 


• Complete DRAM-tester kit In- 


net three-state multiplexer 


cluding programed PAL's, cab- 


IC2, IC3— 74HCT4040 12-stage 


inet, and AC adaptor, KIT 


binary counter 


#DT-90CK— $89.95. 


IC5 — AMD16L8B-2PAL 


• PC board only, #DT-90PCB— 


IC6— AMD 16R4A-4 PAL 


$18.00. 


IC7-— LM7805 5-vo(t regulator 


• Programed PAL's — $7,50 


IC8— LM317LZ low-power adjusta- 


each. 


ble regulator 


• A factory assembled, cali- 


D1-D4 — not used 


brated, and tested DRAM test- 


D5-D8— 1N4004 1-amp rectifier 


er — $119.00. 


diode 


Add 5% shipping/handling charge 


LED1-LED3— red light-emitting 


($4.00 minimum, $10.00 max- 


diode, 1 /a-inch diameter 


imum.) Florida residents must 


LED4 — red/green 3-lead common- 


add sales tax. VISA, MC and 


cathode LED module 


COD-CASH orders accepted. 



38 



a number of discrete logic ICs in 
a single custom-programed IC. 
The PAL device has a program- 
mable and array followed by a 
fixed or array. In the DRAM-test- 
er circuit we use two very com- 
mon PALs, a 16L8 and a 16R4. 
Both are low- power devices, and 
relatively inexpensive. 

The use of PAL's results in re- 
duced parts count and power 
consumption, a smaller PC 
board, faster logic, increased re- 
liability, and, usually overall re- 
duced cost. A reduced parts 
count means less-complex PC 
boards are required, and circuit 
changes can frequently be made 
in the PAL program without af- 
fecting the PC board. On the 
down side, designing with PAL's 
does require support tools con- 
sisting of design software and a 
device programmer. (Those items 
are needed by the circuit design- 
er; the builder does not require 
those items, as programed PAL's 
are available from the source 
listed in the parts list.) The PAL 
design software provides the link 
between high-level logic expres- 
sions and the low-level program- 
ming details which the device 
programmer uses. 

In our circuit, IC5 (a 16L8 PAL) 
has 10 dedicated inputs, 2 dedi- 
cated outputs, and 6 com- 
binatorial input/output pins. IC6 
is a 16R4 PAL which has a 4-bit 
register, a clock register input, 8 
dedicated inputs, 4 registered 
outputs with an output-enable 
pin, and 4 combinatorial input/ 
output pins. Both are 20-pin DIP 
TTL devices, which are one-time 
programmable by opening fuse 
links {with an appropriate device 
programmer) to configure the 
and and or gates within the de- 
vice. The PAL devices implement 
the Boolean logic transfer func- 
tion, the sum of the products. 
The and array creates custom 
product terms, while the or array 
sums selected terms at the out- 
puts of the device. 

Figure 6 shows the pinouts for 
the 16L8 and 16R4 PAL's with the 
input/output signals and logic 
equations used to generate each 
output. Figure 7 shows the logic 
diagram for the 16L8 and Fig. 8 
shows the 16R4. A PAL is man- 
ufactured with all "fuses," or con- 
nections intact. The undesired 
fuses are blown open by the pro- 
grammer, leaving only the desir- 



r- 

Q01 1 

ASEU 2 

IHASi 3 

CKINAl 4 

MTEST l 5 
I 
RDl 6 

Q21i 7 

Q22j 8 

UKINB j 9 

GNDI1Q 
L_. 



IC5 
16LBB-2 



cc 



/" LOGIC EQUATIONS "7 



20 jV, 

191 ERROR 

18HHIGHMARG 

i 
17I1N0RMMARG 

leilLOWMARG 

15DCK0UTA 

1-h'din 

ISi'lGKOUTB 

12UCAS 

11ID0UT 
. I 



DIN 

CAS 

HIGHMARG. 0E 

LOWMARG. 0E 

NORMMARG. 0E 

HIGHMARG 

LOWMARG 

NORMARG 

ERROR 

CKOUTA 

CKOUTB 



IQ21 8 100 1 021 & Q0; 

IASEL S. RAS; 

MTEST h 022; 

MTEST & 1022; 

I MTEST; 

Q22; 

IQ22; 

022 # IQ22; 

RD & RAS & (D0UT & 101 N * ID0UT & DIN); 

CKINA8. 1CK0UTB & l{CKINB & ICK0UTA}; 

CKtNS & ICK0UTA & l(CKINA& ICK0UTB}; 



CKIN i 1 
Q8J 2 
Q9|3 

0181 4 

019! 5 

OK IN! 6 

ICYCLf! 7 

rstIs 

ERROR 1 9 
GNDH0 



IC6 
16R4A-4 



cc 



2DJV, 

191 AS 

18JASEL 

17 [PASS 

16|(AIL 

15 [{UNUSED OUTPUT} 

14t!CK1 

13ilRAS 

12|A9 

11 1 I0E f QUTPUTENABLE" INPUT) 
I 



/" LOGIC EQUATIONS *7 

ASEL = IRAS; 

A8 = IRAS & Q8 * RAS & Q18; 
A9 = IRAS & Q9# RAS & 019; 
RAS = CKO & ICKIN; 
PASS.D= IEAIL&IQ18; 
EAIL.D = ERROR & CKO t RAIL & IRST; 
CK1.D = IRST 8, CK:1 & IR1L & CYCLE; 
b 

FIG. &— PAL PINOUTS AND LOGIC EQUATIONS. 6-a shows the pinouts for the 16L8 and 6- 
b shows the 16R4. The logic equations are used to generate the outputs. 



ed logic connections. 

Assembly 

The DRAM tester is easy to as- 
semble. Parts are installed on 
both sides of a double-sided 
plated-through PC board mea- 
suring 3.35 x 3.8 inches. Pro- 
gramed PAL's, as well as the other 
parts including the PC board, are 
available from the source listed 
in the parts list. The profession- 
al-looking case you see is also 
available at extra cost. Parts as- 
sembly order is not critical, how- 
ever, it's recommended that you 
install all resistors first, then di- 



odes, IC sockets (not including 
the ZIF sockets), IC7 and IC8, 
and then the capacitors. Follow 
Fig. 9 for correct placement of 
parts. 

Next install power-jack Jl, and 
switches SI, S2 and S3. Be sure 
S2 and S3 are straight so that 
they will properly fit in the cab- 
inet openings. Next install poten- 
tiometers R5, R17, and R19; R5 
mounts under the PC board with 
the pins bent upward to fit the 
connection holes from under the 
PC board. 

The two-color (red/green) LED 
(LED4) is probably the most diffi- 



s 
§ 



39 



16L8 






te I3H — 



0< 3 4 7 i 1112 mi Ilia BH A« 31 



'iS-te 



iEHc 



'♦EH*: 



>EHte: 



.B-te 



'jE-Cs: 



lEhfc 



14 7 1 1112 IB If- 1»» 2124 7TU 31 




FIG. 7— 16LS LOGIC DIAGRAM. This 20-pin DIP device Is one- 
time programmable by configuring the and and on gates within 
the device. 



FIG. 8— 16R4 LOGIC DIAGRAM. A PAL is manufactured with all 
"fuses" Intact. The undesired fuses are blown open by the pro- 
grammer, leaving only the desired logic connections. 



CO 

o 
o 

O 



LU 

6 

D 
< 
EC 



cult component to install. Be 
sure to observe polarity; the 
slightly shorter lead is the red- 
LED anode ( + ), the center lead is 
the common cathode (-), and 
the remaining lead is the green- 
LED anode. Holding the LED 
with the shorter lead on your left, 
bend the center lead at a 90-de- 
gree angle, snug against the com- 
ponent body, toward yourself, 
and likewise bend the other two 
leads in the opposite direction, 
spreading them slightly. Align 
LED4 over the proper PC -board 
location and bend the three leads 
down to fit the holes. Check for 
proper alignment with the cab- 
inet before soldering. 

Install LED1. LED2, andLED3. 
Note that the flat side of the LED's 
is the cathode. Allow the LED's to 
stand about % a- inch above the 
PC board. Install the two 2IF 
sockets and insert IC1— IC6 into 
the appropriate sockets. Recheck 
all component connections and 
polarities. If you are satisfied that 
everything looks correct, you're 



ready to continue. Figure 10 
shows a photo of a completed 
board. 

Checkout 

Set R17 and R19 to midpoint 
adjustment. With no device in ei- 
ther test socket, connect a 9-volt 
DC power supply, rated at 200 mA 
or more (the actual current draw 
will be about 150 mA), to Jl. (The 
polarity does not matter as we 
have a diode-bridge power in- 
put.) A continuous red should be 
displayed on LED4, the pass/fail 
indicator. 

Using a DC voltmeter, make the 
following measurements. (Note 
that a ground pad is located in 
each corner of the PC board.) 
These voltages should be within 
± 0,1 volt: 

• IC7 pin 3 (V cc ) should be 5.0V, 

• With the margin switch (S2) off 
(slider to right), measure V DUT at 
TP1. It should be 5.0V. 

• With the margin switch on, the 
low-margin DUT voltage indica- 
tor should be on and TP1 should 



measure 4.5V. 

• Place a DRAM IC in the appro- 
priate ZIF test socket, turn the 
access-time potentiometer (R5) 
fully clockwise and press test- 
switch SI. If the device under test 
is good and the tester is working 
properly, LED4 will blink green 
and, if the margin switch is on, 
the tester should alternate be- 
tween high- and low-margin volt- 
ages. If you do not get a correct 
indication, try a power off and on 
reset. Turn on the cycle switch 
(slider to the left) and the tester 
should repeat the test without 
having to press the test button. 

• When the high-margin voltage 
indicator LED3 is on, the voltage 
at TP1 should be 5.6V. 

If all of the above voltages check 
out properly, only the "speed" or 
access-time calibration remains. 
If you have access to a 100-MHz 
oscilloscope, look at TP4 with no 
IC in either test socket. That is 
the master clock and it should 
run continuously. Allow the unit 
continued on page 60 



40 



DAVID PLANT 



THERE IS AN OLD AXIOM THAT A MANS 

work is only as good as his tools — 
and a good pulse generator is al- 
ways a good tool to have. Those of 
us who don't often need pulse 
generators — the technician 
working at home on a project, for 
example — can usually get by with 
a 555 timer added to a prototype 
board and used as a trigger. But 
there's not always enough room 
on the board to do that, and it is 
always a pain in the neck. 

The solution to that problem is 
our Pulse-Mate, a compact sin- 
gle-shot and continuous-pulse 
generator. The easy-to-use de- 
sign has automatic level setting 
and positive and negative pulse 
output. It can be powered from 
the device under test in the range 
from 4.5 to 18 volts DC, and has 
short-circuit protection for itself 
and the device under test. 

The circuit 

Referring to Fig. 1, the circuit 
basically has three sections. 
Foremost is the actual pulse gen- 
erator built around the ubiq- 
uitous 555 timer, which can be 
switched from monos table mode 
(one shot) to astable mode by S2, 
The value of R8 is selected to 
create an approximate square 
wave at mid frequency range and 
Rll selects the actual rate desir- 
ed. With S2 in the "astable" posi- 
tion, Rll and C2 give a range of 
about 5- to 200-Hz,, which will 
satisfy most needs. (Note that S2 
is part of potentiometer Rll.) If 
you need to generate higher fre- 
quencies, a reduction of C2 can 
bring the range up well above au- 
dio, but at a loss of the low- fre- 
quency pulsing which can be 
quite handy 

With S2 in the "one shot" posi- 
tion, pushbutton SI will trigger 
IC1 for as long as it is held down. 
The timer's trigger input (pin 2) 
is held high by Rl to prevent false 
triggering from hand capaci- 
tance. When the trigger pin is 
brought to ground by SI or keyed 
by the discharge pin (pin 7) in the 
astable mode, pin 3 goes high to 
about 3.3 volts (when IC1 is 
powered from 5 volts). For better 
circuit stability, power to IC1 is 
regulated. 

The second section of the cir- 
cuit consists of Ql and Q2 which 



provide the high-rise-time pulse 
required for digital work. When 
Ql is turned on by the positive 
output of IC1. its collector goes 
low, giving a negative output 
pulse at the probe if S3 is in the 
"low" position. The low output 
from Ql also turns Q2 off: Q2's 
collector now goes high, which 
provides a positive pulse at the 
probe if S3 is in the "high" posi- 
tion. Transistor Q2 also drives 
Q3, which drives indicator LED1. 
Because Q1-Q3 operate at the 
incoming supply voltage, we 
strongly recommend that you use 
2N4400 or equivalent transistors 
rather than garden-variety 
NPN's, as their base-emitter drop 
is less and they have a faster rise- 
time. The Pulse-Mate's output 
waveform is shown in Fig. 2. The 
probe current is limited to under 



5 mA by R6 to protect both the 
device under test and the Pulse- 
Mate. 

The third section consists of a 
voltage regulator consisting of 
Zener-diode Dl and Q4. That 
configuration was used rather 
than the popular three-terminal 
devices, such as the 7805, be- 
cause, when powered from 5 
volts, the regulator's internal 
voltage drop wouldn't leave 
enough to power 1C1. As the sup- 
ply voltage increases beyond 6.2 
volts, the Zener diode conducts 
and limits Q4's output to 6 volts 
for IC1. 

Construction 

A parts-placement diagram is 
shown in Fig. 3, and we have pro- 
vided the foil pattern for the PC 
board if you would like to make 



PULSE-MATE 



This single-shot and continuous-pulse 
generator is inexpensive and easy to 
build, yet it offers automatic level setting 
and both positive and negative pulses. 




y 

z 
o 

cr 

F 
o 

LU 
-I 
LU 

o 
o 




LED1 
O PROBE 




FIG. 1— THE CIRCUIT HAS THREE SECTIONS: the pulse generator built around the 555 
timer, Q1 and 02 which provide the high-rise-time pulse required for digital work, and a 
voltage regulator consisting of Zener-diode D1 and 04. 



light, check the LED's polarity 
and the mounting of Q1-Q4. Pin 
8 of IC1 should show 4.5 VDC, 
Ql's collector should be low (100 
mV or less), and Q2's collector 
should be high (roughly 5 volts). 
Now check the output pulse by 
putting S2 in the "on" position. 
The LED will flash at about 5 Hz, 
and advancing potentiometer 
Rll will increase the flash rate to 
the point where the LED will ap- 
pear to be continuously lit. If 
there is no flashing, check the 
output of IC1 pin 3 for a positive 
pulse (or a continuous high of 
about 3.3 volts if the SI inputs 
are shorted). 

Final assembly 

The prototype is installed in a 
case that fits well in ones hand. 
However, any enclosure measur- 
ing 2x4 inches or larger will do. 
Also, because the case is a hand- 
held size, the probe is mounted 
directly to it. If you use a larger 
case, you may want to mount the 
probe off-board. 

The probe is made from a 2- 
inch screw that is ground to a 
point after first fitting on an ap- 
propriate nut; removing the nut 
will then deburr the screw after 
the tip is ground down. With one 
washer fitted over the screw, it is 
passed through a hole in the case 
and the nut then secures it in 
place (don't tighten it right now). 
By the way, be careful when drill- 
ing the holes in the case; once a 



FIG. 2— THE 2N4400 TRANSISTORS have 
a fast rise-time; here's what the output 
waveform looks like. 



your own — there's also a drilled 
and plated PC board available 
separately or as part of a kit. 

With the exception of SI. S3, 
and the probe, all parts mount on 
the PC board. Note that LED1 is 
mounted on the foil side of the 
board so that it can protrude 
through the front panel as shown 
in Fig. 4. (Mount the LED 3 /is- 
inch above the board so there is 
room to solder it.) Note that Rll- 
S2 is also mounted facing up 
from the foil side. You don't have 
to connect SI, S3, and the probe 
at this time. Take a minute to in- 
spect your work; if everything 
looks alright, the project is ready 
for initial testing. 

Observing proper polarity, con- 
nect 5 volts DC to the board. With 
R11-S2 in the "off position. 
LED1 should be off. Shorting the 
SI inputs with a clip lead will 
turn on the LED. If there is no 



PARTS LIST 

All resistors are Vi-watt, 5% 

R1, R2— 27,000 ohms 

R3, R4— 10,000 ohms 

R5. R6— 1000 ohms 

R7-R9-^170 Ohms 

R1 0—180 ohms 

R11— 10,000-ohm linear potentiome- 
ter with switch 

Capacitors 

C1, C3, C4— 0.1 u.F, ceramic disc 

C2— 4.7 LJ.F, 16 voits, electrolytic 

Semiconductors 

IC1— LM555 timer 

Q1-Q4— 2N4400 NPN switching 
transistor 

D1— 1N4735 6.2-voit Zener diode, or 
equivalent 

LED1 — any color light-emitting diode 

Other components 

S1 — momentary pushbutton switch 

S2— SPST switch (pari of R11 in 
prototype) 

S3— SPOT toggle switch 

Miscellaneous: project case (Radio 
Shack #270-220 or equivalent), 
knob for R11, 2-inch screw with 
washer and nut for probe assembly, 
red and black insulated alligator 
clips, rubber grommet, heat-shrink 
tubing, wire, solder, etc. 

Note: The following items are 
available from Project-Mate, 
2727 West Manor PI., Suite 207, 
Seattle, WA 98199 (206) 
283-4700: A kit containing a PC 
board and all parts including 
probe hardware, grommet, heat- 
shrink tubing, alligator-clip as- 
semblies, and front-panel art- 
work (does not include S1. S3, 
project case, and knob) is $24.50 
plus $2.50 shipping and han- 
dling. A PC board only is $6.00 
plus $2.50 shipping and han- 
dling. WA residents must add 8% 
sales tax. 




h- 



2 INCHES 



HERE'S THE FOIL PATTERN for the Pulse 
-Mate's single-sided PC board. 

hole is made, it's there to stay. 
The leads of R6 should be insu- 
lated with heat-shrink tubing, 



42 




RG. 3— PARTS-PLACEMENT DIAGRAM. Note that LED1 and R11-S2 mount on the foil side 
of the board. 




+ 5V 
IC1 



CLOCK , 

R1± 

I0K> 

■i 11 — 




CLK 



IC1 
'/2 74LS74 

GND CLR 



FIG. 4 — IT'S A TIGHT FIT, but you end up with a neat little handheld instrument. Notice 
how LED1 is mounted on the foil side of the board and protrudes through the front panel. 

except for the ends; one end is 
secured between the head of the 
probe screw and the washer, and 
the nut can then be tightened. 
The other end of R6 is soldered 
directly to the common terminal 
of S3. Leaving the sharpened tip 
of the probe screw exposed, cover 
the length of it with heat-shrink 
tubing. 

Connect S3 and SI to the 
board; the lead length depends 
on the case you use. The power 
leads on the prototype are ar- 
bitrarily 24 inches long. They are 
soldered to the board then 
passed through a grommet in the 
case. Attach the alligator clips to 
the power leads; use red and 
black insulators for positive and 
negative, respectively. The circuit 



R3 
IK 



#& 



R2 
1K 



LED2 — LED1 



FIG. 5— THIS TEST CIRCUIT uses a 
74LS74 positive-edge-triggered flip-flop. 
Triggering the clock input by hand causes 
the LED's to change state in an erratic 
manner. Triggering it with the Pulse-Mate 
causes the LED's to switch back and forth 
predictably. 



board is secured to the front pan- 
el of the case by the mounting 
hardware of potentiometer Rll 
and the wiring to S3. You can also 
use separate mounting hardware 
if you like. 

You may want to make a name- 
plate as a finishing touch for the 
project, although it's best to 
make sure the circuit is working 
properly before labeling. At any 
rate, the one on the prototype 
was made using an aluminum 
nameplate kit sold by Kepro Cir- 
cuit Systems, Inc. (630 Ax- 
minister Dr., Fenton, MO 63026). 
With it, a full-sized positive is 
made by transferring black 
press-on type and other designs 
to a clear piece of acetate. A blue 
panel (cut to 1/2" over-size) is 
contact exposed — like a pho- 
tosensitized PC board — and de- 
veloped. The unexposed portions 
under the transfer patterns are 
washed away leaving a blue panel 
with white lettering. Of course la- 
beling can also be done in a vari- 
ety of other ways including 
engraving, rub -on decals, adhe- 
sive labels, etc. 

Application 

The device can be tested using 
a spare LED. For a positive-pulse 
test, connect the cathode of an 
LED to ground and connect the 
probe to its anode. Pressing SI 
will light the diode. For a nega- 
tive-pulse test, connect the LED's 
anode to 5 volts and its cathode 
to the probe and press SI to light. 
(Note that the LED will not light 
to full brightness in this part of 
the test because R6 limits the 
probe current to 5 mA.) 

If you want to further test the 
device, build the simple circuit 
shown in Fig. 5 using a 74LS74 
positive-edge-triggered flip-flop. 
When power is applied, one of the 
LED's will light. Stroking the 
clock input with + 5 volts in se- 
ries with a IK resistor should 
cause the LED's to change state. 
(They will, but in an erratic way 
because it's virtually impossible 
to generate a clean clock pulse by 
hand. Now connect the Pulse- 
Mate's probe (positive mode) di- 
rectly to the circuit and the LED's 
will switch back and forth predic- 
tably. You now have a useful piece 
of test equipment for trou- 
bleshooting, project building, 
digital experimenting, and what- 
ever else you can think of, R-E 



1 



43 




CO 

o 

z 
O 

CC 
I- 

o 

UJ 

— i 

UJ 

Q 

Q 
< 



Its quick and 
easy to add an 
intercom feature 
to your existing 
home telephones. 

FRANK POLIMENE 



USE YOUR 
TELEPHONES 
AS A HOME 
INTERCOM 
SYSTEM 



INTERCOMS HAVE BEEN AROUND FOR 

many years, providing a valuable 
tool in communications for home 
and industry. Unfortunately 
these systems either require add- 
ed hardware or hours of labor in- 
stalling wires. Responding to 
demand, many manufacturers 
have incorporated the intercom 
as an added feature in their tele- 
phones. However, replacing your 
existing equipment is an ex- 
pense that usually outweighs the 
justification. 

The Phone-Corn project we will 
describe may be used con- 
currently with any touch-tone 
phone system, and it provides 
features that make it practical, 
easy to use, and inexpensive. Be- 
cause it connects to your existing 



telephone equipment, there are 
no unsightly boxes to clutter up 
your desk. 

How it works 

To engage the intercom at any 
time, all you have to do is pick up 
any phone and press the "#" key. 
That causes one or more alert 
modules to sound an alarm, sig- 
nalling other people in the home 
to pick up a phone. If you answer 
a call that comes in for someone 
else, pressing the "#" key will 
place the call on hold, and the 
alarm will sound on the alert 
modules signalling someone else 
in the home to pick up the phone. 
That someone else may then re- 
lease the call on hold by pressing 
the "#" key or talk to you in pri- 



44 




FIG. 1— THE PHONE-COM TAKES ADVANTAGE of a device called a "network interface," 
installed in most newer homes; it is simply a connector box that separates the outside 
phone line from your internal wiring. 



vate before answering the call. 
Since the system is voice oper- 
ated (VOX), the intercom will dis- 
engage and return to normal 
operation after approximately 30 
seconds if no conversation is 
heard. 

The Phone-Corn takes advan- 
tage of a device called a "network 
interface." installed in most new 
homes over the past 10 years. De- 
spite the complicated name, it is 
simply a connector box that sepa- 
rates the outside phone line from 
your internal wiring (see Fig. 1). 
Since a network interface is used 
by the phone company to deter- 
mine whether problems are inter- 
nal or external, a substantial 
premium service charge may be 
imposed if you don't have one. 
Therefore, it is highly recom- 
mended that one be installed, 
even if not for this project. 

Theory of operation 

Ikke a look at the schematic in 
Fig. 2. In the stand-by mode, re- 
lay RY1 is not energized and the 
only connection to the phone line 
is the coupling- capacitor CI. The 




J2-40 



FIG. 2— CONTROLLER SCHEMATIC. The SSI202P is a telephone tone decoder whose 
BCD output is dependent on which tones are present at pin 9. 



CD 



45 



PARTS LIST— CONTROLLER 

All resistors are V*-watt, 5%, un- 
less otherwise noted. 

R1— 600 ohms, Vs-watt 

R2— 1 megohm 

R3-R7— 56,000 ohms 

R8— 220,000 ohms 

R9 — 10,000 ohms 

R1 0—560 ohms 

R11 — 10 ohms 

Capacitors 

C1— 0.01 u.F, 200 volts, ceramic disc 

C2, C3. C5, C6, C1 1—0.01 nR 50 

volts, ceramic disc 
C4 — 22 m-R 16 volts, tantalum 
C7— 0.1 n-F. 50 volts, ceramic disc 
C8, C9— 1000 n-R 16 volts, 

©l©ctrQlvtic 
C10— 10 jjlF, 35 volts, electrolytic 
Semiconductors 
IC1— SSI202P telephone tone 

decoder 
IC2 — MC14049 hex inverting buffer 
IC3— MC14013B dual D-type flip-flop 
IC4— LM555N timer 
IC5— 7805 5-volt regulator 
Q1-Q3— MPSA14 or equivalent 

Darlington transistor 
D3, D4, D7, DS— 1N4148 diode 
D1, D2, D5— 1N4004 diode 
LED1— red light-emitting diode 
BR1— 3N246 full-wave bridge 

rectifier 
Other components 
BZ1— 100-dB Mallory Sonalert 

module 
XTAL1— 3.58-MHz crystal 
RY1— DPDT mini relay, 1-amp 

contacts, 12-volt coil 
T1— 600/600 ohm audio isolation 

transformer 
J1 . J2 — modular telephone jack 
Miscellaneous: 12-VAC 500-mA 

plug-in transformer. PC board, 

project case, etc. 



SSI202P (IC1) is a telephone tone 
decoder whose BCD output is de- 
pendent on which tones are pres- 
ent at pin 9. The two most-sig- 
nificant bits (pins 16 and 17) will 
only be high during a "#" key de- 
pression. The high on pin 7 of 
IC4 and pin 4 of IC2 allow Q3 to 
turn on, thereby energizing the 
audible alarm. The alarm will re- 
main on for as long as the "#" key 
is depressed. 

Pin 6 of IC2 is now low, which 
sends a clock pulse to IC3. That 
transfers the high at IC3 pin 2 to 
the output at pin 1, which ener- 
gizes the relay through Ql, R5, 
m and IC2. The trigger input of IC4, 
o also being low, starts the VOX- 
§ timer IC4." The clock pulse to IC3 
°E is delayed slightly by R7 and C2 
o until the output of IC4 pin 3 has 
rjj enough time to remove the reset 
6 signal at IC3 pin 4. When the "#" 
g key is released, pin 11 of IC3 goes 
ec high and toggles the output of 




FIG. 3 — ALERT MODULES plug into any phone jack; the circuit is only active during an 
"off hook" condition to conserve battery power. 

PARTS LIST— ALERT MODULE 



All resistors are 1 A-watt, 5%, un- 
less otherwise noted. 

R1— 2.2 megohms 

R2, R4, R8— 220,000 ohms 

R3 — 10 megohms (see text} 

R5— 56,000 ohms 

R6— 33,000 ohms 

R7— 680,000 ohms 

R9 — 1 megohm 

R1 0—100 ohms (see text) 

Capacitors 

C1 — 0.01 (J.F, 500 volts, ceramic disc 

C2 — 1 n_F, 16 volts, electrolytic 

Semiconductors 

IC1— SSI202P telephone tone 

decoder 
Q1, Q2, Q4— MPSA14 or equivalent 

Darlington transistor 
Q3— 2N5401 or equivalent PNP 

transistor 
D1-D3— 1N4004 diode 
D4, D5—1N41 48 diode 
Other components 
B1— 9-volt alkaline or 7.2-volt Ni-Cd 

battery (see text) 
XTAL1— 3.58 MHz crystal 
BZ1— 100-dB Maliory Sonalert 

module 



PL1 — 4-wire modular phone plug 
Miscellaneous: 9-volt battery con- 
nector, PC board, project case, etc. 
Note: The following items may be 
purchased from BCT Elec- 
tronics, 8742 Belair Road, Bal- 
timore, MD 21236 (301) 256-0344. 
MC/ViSA, AX, and DISCOVER 
accepted. Add $2.50 S&H for 
each total order. 

• Drilled, etched, and screened 
controller PC board — $7.95 

• Drilled, etched, and screened 
alert module PC board— $4.95 

• SSI1202P IC— $11.95 

• Complete controller kit (in- 
cludes PC board and all compo- 
nents except phone jacks and 
housing) — $39.95 

• Complete alert module kit (in- 
cludes PC board and all compo- 
nents except phone plug and 
housing)— $24.95 

Network Interfaces may be pur- 
chased at Radio Shack or most 
electronic suppliers for around 
$5.00. 



B— ^R9 . — R10 — 

Q2 pitttcooeop-p 

' D5 4- h RY1 



' ceb ic.3 C3t ) iw cm-f-Jt } 

-Re- <"■' ~ C1 ^ 5Z 

!C P 'C2 Jt f BZ1 Y + eC8^ + nC : 




J2 

-■ — °RED 



>J1\ 
>J2/ 



GREEN 



jczcji 



m 



J .!} YELLOW 



BLACK 



04 



^-R2 — °i\\ 

C5 ) Jfii— » ' I 



ICS 




FIG. 4— PARTS-PLACEMENT DIAGRAM for the controller. It can be installed in any kind of 
case you can find. 



46 




FIG. 5— THE FINISHED CONTROLLER BOARD is very neat and compact, so it doesn't 
take up much space. 



PHONE LINE 



PHONE LINE 




IC4 pin 3 returns to a low state. 
That places a high on the reset 
pin (pin 4} and the set pin (pin 8) 
of IC3, which turns off RY1, re- 
turning the system to the stand- 
by mode. Any calls in process are 
held by maintaining central-of- 
fice loop current through Rl 
while in intercom mode. 

Alert module 

Alert modules plug into any 
phone jack (see Fig. 3), and can 
be powered by either a 7.2-volt 
rechargeable Ni-Cd or 9-volt al- 



F1G. 6— PARTS-PLACEMENT DIAGRAM 
for the alert module. It's good to have at 
least one on every floor in your home, in a 
central location. 

IC3 pin 13 to a low state, prevent- 
ing the alarm to sound during 
the next depression of the "#" key 
(manual turn off). 

If conversation continues, IC4 
is prevented from time-out 
through C7 and Q2. If con- 
versation stops for more than 30 
seconds, C4 charges to the 
threshold voltage at IC4 pin 6 and 




FIG. 7— A FINISHED ALERT MODULE. It 
can plug into any ordinary phone jack; 
use a T-connector if you must connect 
both a phone and an alert module to the 
same jack. 



kaline battery. However, the cir- 
cuit is only active during an "off 
hook" condition to conserve the 
battery. During normal opera- 
tion, there is approximately 50 
volts on the phone line. That al- 
lows base current to flow through 
Rl which turns on Ql and holds 
Q2 in an off state preventing 
power to IC1 and the audible 
alarm. When the line voltage falls 
below 10 volts, as evident in an 
off-hook condition, Q2 turns on, 
thereby placing IC1 in the stand- 
by mode. 

Telephone tones are decoded by 
IC1 as previously discussed. A 
"#" key activation will activate 
the alarm. Diode Dl is important 
in that it protects IC1 and the rest 
of the semiconductors from 
damage when the AC ringing 
voltage is present on the phone 
line. If you're using a rechargea- 
ble battery, charging current is 
supplied through R3 during on- 
hook conditions. 



Construction 

The Phone-Corn controller is 
built on one PC board, and the 
alert modules are built on sepa- 
rate boards. Determine the 
number of alert modules you will 
need including the master con- 
trol unit. The modules are loud 
enough to cover approximately 
1000 square feet each, even when 
placed behind furniture. It is rec- 
ommended that one module be 
installed in a central location on 
each floor of your house. Con- 
struction is straightforward, 
however, care should be taken 
when handling the static-sen- 
sitive decoder chips. 

We have provided foil patterns 
for both boards, although the 
project can be built using point- 
to-point wiring. Double check 
your wiring before connecting 
the modules to the phone line if 
you don't use the boards. Figure 
4 is a parts -placement diagram 
for the controller board. The 
finished board, shown in Fig. 5, 
can be installed in any kind of 
case you see fit. 

The values for R3 and RIO de- 
pend on what type of battery you 
are using. Use 10 megohms for 
R3 and 82 ohms for RIO for a 9- 
volt alkaline battery. If a re- s 
chargeable battery is used, ^ 
change the value of R3 to 82K g 
and RIO to 10 ohms. Any audio 2 



47 




THE CONTROLLER BOARD is double-sided; here's the component side shown at actual 
size. 



w 
o 

z 
o 

a 

H 
O 

LU 
_l 
LU 

6 

Q 
< 

EC 




SOLDER SIDE of the controller board shown at actual size. 



transformer with approximately 
a 500-ohm primary may be used 
for Tl. 

Figure 6 is a parts-placement 
diagram for the alert module, 
and Fig. 7 shows a finished unit. 
Again, the board can be installed 
in any case you like. 

Follow the red/green color code 
shown in Figs. 2 and 3 when con- 
necting the system to the phone 
line. A "T" adapter may be used if 
you need to connect additional 
equipment to the same jack. 
Velcro strips offer an easy way to 
secure the modules to a wall. 



Installation and check out 

Determine where your network 
interface is by locating the area 
where the phone line enters the 
house. In some cases, the device 
is mounted on the outside. It is a 
small box with a short wire loop 
connecting to a modular jack. Re- 
fer back to Fig. 1 on how to install 
a network interface if it's not al- 
ready present. During the next 
few steps, your phone system will 
be inoperative until installation 
is complete. 

Disconnect the short wire from 
the jack on the network inter- 




-1"/i«IHCHE5- 



FOIL PATTERN for the alert module, also 
shown at actual size. 

face. Connect that wire to J 1 on 
the main control module. Make 
sure all phones on the same ex- 
tension are on-hook, and con- 
nect the controller to a 12-volt AC 
source. Pick up a telephone re- 
ceiver and press the "#" key. The 
alarm will sound and the LED 
should be on. You will also be able 
hear yourself talk through the 
handset. Hang up the phone. 
The LED should remain on for 
approximately 30 seconds, then 
turn off. 

Connect the remaining wire 
from the main control module to 
the jack on the network inter- 
face. Pick up the receiver again 
and initiate a call to determine 
normal operation. If you are un- 
able to dial out, the red and green 
wires (tip and ring) have been re- 
versed somewhere in the system. 
Remember that positive phone- 
line voltage must be present at J2 
pin 2. 

It may be necessary to toggle 
the "#" key once or twice to get 
everything going when the sys- 
tem is first installed or after a 
power failure. Install the alert 
modules and determine the cor- 
rect polarity by measuring a 
positive voltage at the anode of 
Dl. Reverse the wires in the mod- 
ule if it turns out to be necessary. 
If a rechargeable battery is used, 
you should allow it to charge for 
at least 24 hours before activat- 
ing the system. r-e 



48 



The SG3524/5/6/7 IC 

Figure 1 shows the internal cir- 
cuit of the switching regulator IC 
SG3524. In that circuit, the os- 
cillator produces both ramp and 
pulse outputs. Ignoring the cur- 
rent limit (CL) and shutdown cir- 
cuits for the moment, the 
comparator's output goes high 
when the ramp exceeds the out- 
put of the error amplifier. The 
nor gates then go low. turning 
the output transistors off. 

Each nor gate can be high only 
when its three inputs are low. 
The oscillator output toggles the 
flip-flop, enabling one gate, and 
then the other to respond to the 
comparator. That action gates 
one transistor on at a time, 
providing push-pull operation. 
The selected transistor turns on 
at the start of each cycle, and 
turns off as soon as the ramp ex- 
ceeds the error signal. At the end 



IN OUR LAST EDITION. WE EXAMINED 

the basics of switching regulator 
power supplies. Now we'll dive 
into some real-world applica- 
tions. We'll examine the 3524/5/7 
and 3842 IC families in detail, 
summarize others, and show 
some typical circuits. In the pro- 
cess we'll study how to select 
components for those circuits 
and learn more about how 
switching regulator IC's are pro- 
tected against such problems as 
startup current surges, under- 
voltage, and overload. We'll finish 
up with some basic troubleshoot- 
ing hints. 

Lets first start off with an ex- 
planation of the standard no- 
menclature used in naming the 
IC's we will discuss in this article. 
The first digit "1" indicates full 
military temperature range of 
-55 to I50°C, "2" indicates an 
Industrial temperature range of 
-25 to 85°C, and "3" is a com- 
mercial temperature range of to 
70°C. Hereafter, we will refer only 
to the commercial version IC's, 
with prefix "3. " Keep in mind that 
all those IC's are also available in 
military and industrial versions. 
A suffix of "A," "B." or "C" indi- 
cates an enhanced version of the 
IC, which we will discuss in more 
detail later in this article. 

Manufacturers may use many 
different prefixes, some of which 
include 

SG— Signetics. SGS-Thomson, 
Motorola, and Linear Technology. 
CS — Cherry Semiconductor. 
XR— Exar. 
CA— GE-RCA. 
IC— IPS. 

LTSG— Linear Technology. 
LM — National Semiconductor. 
UC — Unitrode. Motorola, Linear 
Technology, and Signetics. 
UD— SGS-Thomson. 
IP— IPS. 
LAS — Lambda. 



Well take an 
in-depth took at two 
switching regulator IC jf 

families, with some applica- 
tions, and guide you through 
basic troubleshooting techniques. 



of each cycle, the oscillator pulse 
momentarily forces both gates 
low, protecting against the pos- 
sibility of both transistors being 
on at the same time. 

The current-limit amplifier 
protects against current over- 
loads. Its output is an open-col- 
lector type — open-circuit when 
high, pull-down to ground when 
low. The current-limit amplifier 
and the shutdown transistor can 
be used to force the comparator 
output high, shutting down both 
transistors. 

Figure 2 shows the SG3524 in 
a simple DC-DC converter. The 
oscillator frequency of about 60 
kHz is set by R5 andC2. (The flip- 
flop divides the push-pull output 
frequency to 30 kHz.) The cur- 
rent-limit amplifier goes low 
when its input exceeds 0.2 volts, 
limiting Rll's current to 2 amps 
in case of overload or transformer 



Inside 

SWITCHING 
POWER 
SUPPLIES 



HARRY L. TRIETLEY 




HIINPUT-\2/ 
COMPEMSWION,'^ 

y 

CURRENT f .- 

+ LIMIT SENSE - 



CURRENT _ 
-LIMIT SENSE 




SHUTDOWN -t 10 t 

S' 






Sfb/WVJ 



Rr-C 6 1- 



OSCILLATOR 



SND 



14 (-EMITTER I 

' — " — "^ — JL ^-"-x OSCILLATOR 
-^ 3 t OUTPUT 
T 

I 
I 






FIG. 1— INTERNAL BLOCK DIAGRAM of the SG3524 switching regulator IC. 



+28V-«- 



"*M- 



-VA—*- 



R1 



C1 
.1 



R4 
5K 



16 



R5 
2K 



C2 
.01 



15 



INV 

Nl 

Vref 
R T 

osc 



SG3524 



Cl+ 



-^ SHUT ROUP 

DOWN GND 0UMK 



12. 



n 




R11 
0,1 



C3 R10 

.001 20k: 



lOOfipf 1 



FIG. 2— THE SG3524, TWO SWITCHING transistors, a transformer and a few components 
create a complete 5-volt push-pull switching regulator. 



en 

o 

2 

O 

5 
P 

o 



LU 

Q 

Q 

< 



saturation. Transistors Ql and 
Q2 are used for switching trans- 
former current. (The on-chip 
transistors are rated at only 100 
mA.) Supply pulses produced by 
the circuit are filtered by C4. 

The output of the error ampli- 
fier is proportional to the dif- 
ference between the reference 
input (pin 2) and the feedback 
(pin 1). If the output increases, 
the error voltage drops. The ramp 
then reaches the error voltage 
more quickly and the transistors 
ttirn off sooner, until the output 



is reduced back to 5 volts. Since 
the feedback voltage and ground 
are directly connected, input-to- 
output isolation is not provided. 
Resistors R6 and R7 limit the 
current through the internal 
drive transistors, which are used 
to switch Ql and Q2. Frequency 
compensation for closed-loop 
stability is provided by RIO and 
C3. Transistors Ql and Q2 
should be high-speed switching 
power transistors rated at least 5 
amps and 60 volts. Shottky or 
fast-recovery diodes should be 



used for Dl and D2. Because the 
output is balanced, the trans- 
former core does not need to be 
gapped, a small ferrite core will 
do. 

At high frequencies, the equiv- 
alent series resistance (ESR) of 
filter capacitor C5 is higher than 
its capaci Live impedance. Low se- 
ries-resistance electrolytics 
should be used, preferably capac- 
itors designed specifically for 
switching supplies. 

The enhanced SG3524A 

Figure 3 shows the enhanced 
version SG3524A, which is pin- 
compatible and interchangeable 
with the non-A version. The en- 
hanced version adds an under- 
voltage lockout circuit which 
disables the regulator until its in- 
put rises above 8 volts. That 
holds current drain to standby 
levels during turn-on, guarding 
against problems during startup, 
surges, and brownouts. A pulse- 
width modulator latch is also 
added, which eliminates multi- 
ple pulsing in noisy environ- 
ments. Set by the comparator 
and reset by the clock pulse, it 
can switch only once per com- 
parison cycle. 

Further protection is provided 
by thermal protection circuitry 
(not shown). Performance speci- 
fications also are improved — the 
5-volt reference is trimmed more 
closely ( ± 1%) and the error am- 
plifier's output can swing up to 
the 5-volt rail. 

Let's look at one more member 
of this family, and an application. 
Figure 4 shows the workings of 
the SG3525A/7A. The 3525A and 
3527A differ only in their output 
logic; the 3525A is low when off 
while the 3527A is high when off. 
(The pinouts of the 3525A/7A do 
not match those of the 3524 IC 
series.) 

Operation is similar to the 
3524, but with added features. 
The oscillator has a sync input, 
making it easy to lock the fre- 
quencies of several supplies, 
eliminating problems with beat 
frequencies in multiple-supply 
boards or systems. The shut- 
down circuit (also included in the 
3524A) and soft-start feature 
simplify the design of protective 
circuitry, as will be seen in the 
next application. The totem pole 
(push-pull) outputs, rated at 
maximum 500 mA, provide fast, 



50 



I 
T 

OSC-* 3 / 

T 

R T -i 6 t 

V 







S>J2 



osc. 



UNDER- 
VOLTAGE 
SENSOR 




-5V 
REFERENCE 
REGULATOR 



CLOCK 



POWER TO 
INTERNAL 
CIRCUITRY 



RAMP 



COMP-f 9 i- 

INV ^ 
INPUTH T l- 



Nl INPUT/ £y 

current;' Jy 



^ 



UMIT -„- 
- CURRENT' Jf ^ 



LIMIT 
SENSE 



I 

L. 





COMP 



rf 1 



o 

Q-, 



Ql 




1 

-M6>-Vf<e 

r 
i 
i 
I 
i 

A 



S F 
PWM 
LATCH 



«* 



U2 




£ 



R1 
1K 



R2 
10K 



SG3524A 



I 

isVq, 

i 
i 
i 
i 

4 14 I- Eg 
V 

//gVSHUT 
«"_ J DOWN 

8 _H3N0 



" 1 



FIG. 3— THE SG3524A IMPROVES the basic device by adding undervoltage lockout, a 
pulse-width modulator (PWM) latch, thermal protection, and improved reference ac- 
curacy. 



DISCHARGE-* 



COMPENSATION^ 9 
T 

INVINPUT— l v 1 



HI SNPUT^Z/ J ~^ R J™ R 



r 
I. 



SOFT-START -H 



SHUTDOWN -4 101- 



5K 




FIG. 4— THE SG3525A AND SG3527A PUSH-PULL switching regulators provide 50O-mA, 
totem-pole outputs and oscillator synchronization. 



solid switching for high and low 
transitions. The 3524s separate 
current-limit amplifier has been 
omitted. 



Figure 5 shows a 15-watt DC- 
DC converter. The 200-kHz fre- 
quency (100 kHz final output) is 
set by R2-C2. The internal dis- 



charge transistor (pin 7) allows 
control of the discharge time at 
the end of each ramp. That pro- 
vides an ensured stoptime be- 
tween output pulses so that, even 
with switching delays, both tran- 
sistors cannot be on at once. A 
47-nanosecond time constant is 
provided by R16-C2. 

The 5-volt reference (pin 16) is 
connected to the noninverting 
input (pin 2) by current limiting 
resistor R3, while C9 provides 
high-frequency bypassing. Nega- 
tive feedback voltage is divided by 
R1-R4, dividing the 6-volt output 
down to 5 volts. The basic theory 
of operation is similar to that of 
Fig. 2: the ramp is compared to 
the error signal to control the on- 
off switching of the outputs. On 
each cycle, the internal flip-flop 
selects either output A or B. The 
selected output is switched high 
at the start of each ramp and re- 
set to low by the latch when the 
ramp voltage exceeds the error 
amp's output. As in Fig. 2, the 
direct feedback connection 
means there is no input to out- 
put isolation. 

Compensation for closed-loop 
stability is provided by R6. R7 
and C4. Switching spike cur- 
rents are limited by RIO, Rl 1 , and 
R12 in the output stages. Compo- 
nents C5 and Rl 7 act as a "snub- 
ber," limiting switching tran- 
sients from the primary. 

When input power is first ap- 
plied, Ql will be off and soft-start 
capacitor C3 will be discharged. 
As C3 is charged from the inter- 
nal 50-uA current source, its 
voltage will rise, gradually in- 
creasing the voltage to the pulse- 
width modulator (PWM) control's 
bottom input. That gradually in- 
creases the amount of time per 
cycle that the output is turned 
on, providing a "soft" rise of the 
output voltage, which allows the 
filter capacitors to charge slowly, 
reducing startup current surges. 

If R9s current exceeds about 3 
amps (0.7-volt drop), Ql will turn 
on, energizing the shutdown cir- 
cuit which pulls pin 8 low and 
discharges C3. As the current 
drops below 3 amps, Ql turns off, 
C7 discharges, the shutdown in- 
put goes low and the soft-start 
capacitor provides a "soft" recov- 
ery for the power supply. 

Power transformer Tl is 
wound on an EE25 ferrite core 
(0.25-inch center leg). It feeds a 



I 



+ 12VO- 



R4 
1.5K 



( 1 CI 
T"1(%F 






FB 
+ 6V 



R6 
470K 



IS 



R5 £ I ^ 

1.2KS C7 R15 /xj\ .I 

R10 "1 isn f T-M- 

1011 ± % I *&-■ ■ * £/ 01 



13 



10 



SHUT 



2NZ907 R1? 



INV 

CMP GND REF 



R7 
3.3K 



IC1 
SG3S25A 

Nl Ct PIS r t 



SS 



9 



C4 
.01 



J 

R1 
8.2K 



1? 



IB 



R3. 

1.2K; 



r 



R16 
47U 



C9 



X 



£ 



C2- 
.001^ 



6 



R2 
S.6K 

C3-L 
1uF*~ 




FIG. 5— A PUSH-PULL SWITCHING REGULATOR produces plus and minus 6 volts at 15 
watts. 



to 
o 

z 
o 

EC 

o 

LU 

_l 

LU 

o 
< 

rr 



conventional full-wave bridge, 
providing + and - outputs. 
Coupled inductor T2, consisting 
of two coils wound on a cylin- 
drical ferrite core, and the output 
capacitors filter the output to 50 
millivolts peak-to-peak. Tran- 
sistors Q2 and Q3 are 50-volt, 5- 
amp, N-channel power 
MOSFETs. Fast-recovery diodes 
must be used in the rectifier due 
to the high frequency; Dl— D4 are 
100-voIt, 8-amp diodes with 35- 
nanosecond recovery. 

Current-mode regulators 

We now turn to a different class 
of switching regulators — current 
mode. Although the basic operat- 
ing theory remains the same 
(pulse-width modulation), cur- 
rent-mode switching regulators 
differ in that the internal ramp is 
eliminated. In its place, the 
ramp-like increase in the trans- 
former's inductive current is 
used for control. 

Figure 6 shows the basics of a 
current-mode comparator. The 
pulse from an R-C clock sets the 
flip-flop, producing a high out- 
put. FET Ql turns on and trans- 
former current begins to flow. As 
the inductive current ramps up- 
ward, the feedback from current- 
sensing resistor R2 increases. 
Eventually, the feedback voltage 
equals the error amplifier's out- 
put, at which point the com- 
parator resets the flip-flop, Ql 
then turns off until the next clock 
pulse. 

As with previous regulators, 
the feedback voltage, V FB , repre- 
sents the filtered output. If the 
feedback becomes lower or high- 



+5V 




• Ftl 



CLOCK 



T 



ERROR 
AMP 



ERROR 
COMPARATOR 




03 



CLOCK i i 


FET _^TL 


S\ 


. __r^L 


-—^ERRCm 


COMPARATOR 


1 



3fR2 



FIG.6 — A CURRENT-MODE comparator uses the current feedback signal as the ramp, 
providing pulse-by-putse current limiting. 



er than the reference voltage, the 
error signal will increase or de- 
crease accordingly, increasing or 
decreasing the on time until the 
proper voltage is restored. 

Current-mode regulation of- 
fers two major advantages; pulse- 
by-pulse current limiting, and 
feedforward line regulation. 
Notice that the circuit in Fig. 6 
contains no current-sensing 
comparator. Instead, each cur- 
rent pulse ends as soon as it ex- 
ceeds the level set by the error 
amplifier. No matter what the 
cause of overload, whether trans- 
former saturation, an output 
short, or input overvoltage, the 
circuit will limit current in- 
stantly. Pulse-by-pulse limiting 
also eliminates the need for a sep- 
arate soft-start circuit. 



FEEDFORWARD UHE REGULATION 
CLOCK 



»m r 






-- -i ERROR 



FIG. 7— FEEDFORWARD compensation of 
input variations is achieved when the 
ramp rate of the transformer's primary 
current increases as the input voltage in- 
creases. 

Feedforward line regulation is 
illustrated by the waveforms 
shown in Fig. 7. With a fixed load, 
the input voltage suddenly in- 
creases. On the very next pulse, 



52 



the inductive current, I, ramps 
more quickly due to the in- 
creased transformer voltage. 
Since the feedback and the error 
signal have not changed, the lim- 
it is reached more quickly and 
the pulse width becomes shorter. 
Changes in line voltage are, 
therefore, compensated before 
they have a chance to affect the 
output. 

UC3842/3/4/5 

Figure 8 shows the block di- 
agram of current-mode PWM 
controller IC UC3842. Compared 
with the circuit in Fig, 6, the 
UC3842 adds an undervoltage 
lockout and an output nor gate. 
The undervoltage lockout, with 
hysteresis, disables the output 
pulses until V cc rises above 16 
volts. Once started, it will not 
drop out unless V cc goes below 
10 volts, a feature which prevents 
constant toggling between "oper- 
ate" and "lockout." When dis- 
abled, the output (pin 6) goes to a 
high-impedance state. A 
"bleeder" resistor should be con- 
nected from pin 6 to ground to 
prevent leakage current from 
turning the switching FET on. 

The output nor gate imple- 
ments lockout, but also serves 
another protective function. 
When the oscillator pulse is high, 
the nor output will be low, the or 
output high, and pin 6 low. The 
output cannot go high until the 
clock goes low. The clock is set up 
so that timing capacitor CI 
charges through Rl, and dis- 
charges through the constant 
current sink. By choosing a 
larger capacitor and smaller re- 
sistor, the charging time (clock 
low) can be decreased and the 
discharge time (clock high) in- 
creased. That allows you to estab- 
lish the maximum on time, or 
duty cycle, which is especially im- 
portant in circuits where duty cy- 
cles higher than 50% can lead to 
transformer core saturation. 

The D2-D4-R1-R2 network be- 
tween the error amplifier and the 
current-sensing comparator re- 
duces the error signal so that ex- 
cessive power is not lost in the 
current-sensing resistor. The 
one- volt Zener diode clamps the 
error signal so the maximum 
turn-off level will never exceed 
one volt. 

UC3843 is similar to the 3842 
but has a lower lockout voltage. 




COMP-l 1 i 

V 

CURRENT^' , v 
SENSING v^ 

FIG. 8— INTERNAL BLOCK diagram of the UC3842 current-mode switching regulator IC. 
The UC3843 IC is similar but operates with a lower undervoltage lockout. 




FIG. 9— THIS OFF-LINE CURRENT-MODE regulator produces isolated + 5 volts and ±12 
volts from 11 7- volt line power. 



Intended for use at lower volt- 
ages, it operates at 8.4 volts, and 
drops out at 7.9 volts. UC3844 
and UC3845 (not shown) have 
one added feature; a flip-flop 
which disables the output on al- 
ternate clock cycles. That guar- 
antees the duty cycle will always 
be less than 50% for circuits 
where that is critical. 

An off-line flyback converter 

Figure 9 shows an SGS-Thom- 
son UC3842 IC in an "off-line" 
flyback regulator. The circuit pro- 
vides + 5 volts at 4 amps and ±12 
volts at 300 mA, and can deliver 



27 watts. 

The term "off-line" means that 
the regulator is on the primary 
side of the transformer and oper- 
ates directly "off the line." The 
primary advantage of such a cir- 
cuit is that large amounts of 
power can be coupled through a 
small, high-frequency trans- 
former. Line operation requires 
high-voltage transistors and di- 
odes, and prevents direct coup- 
ling between the output and the 
feedback circuit. 

The line voltage is rectified and 
filtered by BR1 and CI. Initial 
startup current to the IC is pro- 



s 
5 



53 



vided by Rl . The UC3842's under- 
voltage lockout circuitry prevents 
startup until the voltage on C2 
reaches 16 volts. The 50-kHz op- 
erating frequency is set by R6- 
C6. with a maximum duty cycle 
of about 95%. The internal 5-volt 
supply is filtered by C5 to elimi- 
nate switching spikes. Current- 
mode feedback is provided by 
RIO, while C14 and R5 are used 
for frequency compensation. 

Once the circuit has started, 
voltage feedback comes from the 
10-turn control winding. The 
voltage at pin 2 is compared to 
the internal 2. 5- volt reference. 
The voltage difference increases 
or decreases the duty cycle until 
the voltage at pin 7 equals 13.1 
volts. Allowing for diode voltage 
drops, that corresponds to a peak 
voltage of about 14.6 volts on the 
control winding. The control-to- 
secondary turns ratios are 
chosen to produce 5- and 12-voIt 
DC outputs. Notice that control 
is from the control winding's volt- 
age, the outputs are only indi- 
recdy regulated. Power losses due 
to currents in the windings, di- 
odes and inductor will affect the 
outputs. Five-volt regulation is 
10% accurate, while the ± 12-volt 
regulator has 5% accuracy. 

Transistor Ql is a 500-volt, 5- 
amp power MOSFET. The diodes 
are fast- recovery diodes. A "snub- 
ber" network is formed by D3-C9- 
R12 to hold turn-off spikes below 
Ql's breakdown voltage. Snubber 
D4-C8-R11 slows the turn-off rise 
time until Ql's current has had a 
chance to decay. 

Transformer design is impor- 
tant; the air gap must be large 
enough to prevent core satura- 
tion but small enough to main- 
tain the required inductance. 
(Note that an air gap is not 
needed in balanced push-pull cir- 
cuits.) In the Fig. 9 circuit, an 
EC35 ferrite core is used ( 3 /s-inch 
dia. center leg, Ferroxcube 
EC35-3C8) with a 0.5 mm gap in 
the center leg. 

The primary winding consists 
of 45 turns of 26 AWG wire. The 
m 12-volt windings are each 9 turns 
Q of 30 AWG wire, wound together 
o (binlar). The 5-volt secondary is 
fE only 4 turns, but instead of using 
fj> a heavier gauge wire, four binlar, 
uj 4-turn windings of 26 AWG wire 
6 are used, with their ends con- 
es nected in parallel. The control 
ce (feedback) winding consists of 



two bifilar, parallel 10-turn 30 

AWG windings. Now let's take a 
look at how an op to isolator can 
be used in a switching regulator. 

Optocoupled feedback 

Optocouplers provide a conve- 
nient way of coupling isolated 
feedback. Figure 10 shows a cir- 
cuit in which the 5-volt second- 
ary of a switching regulator is 
controlled. If the output goes 
above 5 volts, the inverting input 
decreases below 2.5 volts and the 
optocoupler's LED current de- 
creases. That decreases the cou- 
plers output transistor current, 
increasing V FB until the isolated 
output returns to 5 volts. 



+5V 




+V FB ' k IC1 

input Jr,, 

COMMON J^.-- 



,, Hi 

| R2 10K 



R4 
10K 



OUTPUT 



COMMON 



R5 
10K 



> D2 

* LM385' 

< -Z.SV 



FIG. 10— OPT0C0UPLER FEEDBACK al- 
lows precise control of an isolated output. 



A wide selection of IC's 

Once a new IC technology is es- 
tablished, the offerings multiply 
as designs advance and the mar- 
ket expands. Switching reg- 
ulators are no exception. Voltage 
mode, current mode, single- end- 
ed and push-pull IC's cover a wide 
variety of power levels and user- 
specific applications. 

Table 1 summarizes some of 
the many IC families available. 
Most of the devices shown can be 
multiple-sourced. The part 
number prefixes vary from man- 
ufacturer to manufacturer, and 
many offer additional, proprie- 
tary devices. 

It's not possible to fully de- 
scribe all devices in an abbrevi- 
ated table, but the listing should 
help direct you to data sheets for 
IC's to meet your needs. The 8- 
pin devices tend to be simpler to 
apply, while the 16-pin and larger 
IC's generally offer more compli- 
cated protective and "housekeep- 
ing" features. 

The 3524/5/7 and 3842-7 fam- 
ilies have been fully covered in 
this article. The 4191-3 family. 



with its low operating voltage 
and 200- u-A current drain, is ide- 
al for battery and micropower ap- 
plications. Companion micro- 
power device 4391 provides 
regulated negative outputs from 
positive supplies. LT1070 is the 
only IC in the listing housed in a 
power IC package. 

Troubleshooting hints 

When troubleshooting switch- 
ing regulators, always begin with 
the obvious. Check for input 

power and output shorts, broken 
wires, defective connectors, sol- 
der bridges, defective solder 
joints, bad copper traces, 
scorched components, and so 
on. It's surprising how often a 
good visual inspection can un- 
cover a problem. 

Make sure you have a data 
sheet, pinouts of the control IC, 
and a circuit schematic, prefera- 
bly with voltages and waveforms. 
There is such a wide variety of 
IC's and operating modes that it's 
difficult to troubleshoot on an in- 
tuitive basis. Figure 11 shows a 
"generic" block diagram, which 
may help you to think through 
the circuit function-by-function. 

When breadboarding tempo- 
rary components, remember that 
switching regulators produce 
fast, high-current pulses. Con- 
ductor size and lead dress are im- 
portant. The input filter capaci- 
tor should be close to the IC , not a 
foot away If the main source of 
power is at a distance, add a sev- 
eral hundred microfarad input 
bypass capacitor next to the IC. 

Even though you may under- 
stand the operation of switching 
regulators, troubleshooting 
them can be difficult. The IC and 
its circuitry perform many func- 
tions, and the failure of one can 
cause improper operation of the 
rest. For example, failure of the 
feedback circuit may lead to over- 
voltage, overcurrent, and shut- 
down by one of the protective 
features. Is the circuit dead, un- 
stable or out of regulation? That 
alone may often narrow the 
search to one particular part of 
the circuit. 

The following hints may help 
you pinpoint the problem to a 
specific area of the circuit. After 
the visual inspection, check the 
output for shorts or overloads 
and check the input source, rec- 
tifier, filter, and transformer. 



54 



TABLE 1— A SUMMARY OF SELECTED SWITCHING REGULATOR IC'S 



IC 

Family 



Manufacturers* 



Mode 
Vorl 



Output 
(Single 
or Push- 
Pull) 



Package 



Supply 



■out 

Max 



Reference 



Comments 



3524/5/7 



CS, ERIC, EXAR, 

GE, IPS, LT. MOT, 

NAT, SGS, SIL, 

SLG, Tl, UNI 



P-P 



16 Pin 



S-35V 



100mA 



5 or 5.1V 



See Article. 



3842-7 



CS, ERIC, IPS. 

LT, MOT, SGS, 

SIG, Tl, UNI 



8 Pin 



8(or16)-25V 



1A 



5V 



See Article. 



4191-3 



MAX, RAY 



8 Pin 



2.4-30V 



150mA 



1.31V 



Micro power for battery 
applications, 200 p A 
quiescent supply 
current. 



4391 



MAX, RAY 



8 Pin 



- 4 to - 30V 



100mA 



1.25V 



Inverting, micropower 
for battery applications, 
250nA supply at 4V 



5560 
5562 

5561 



CS, IPS, SIG 



16 Pin 
20 Pin 

8 Pin 



10.5-18V 
10-16V 

10.5V-18V 



40 mA 
100mA 

20mA 



3.72V 
3.80V 

3.75V 



Full -featured, 
flexible. 

Lower cost, fewer 

housekeeping 

functions. 



493/4/5 
593/4/5 



CS, EXAR, 

GS, IPS, 

MOT, NAT, 

Tl, UNI 



P-P 



16 or 

18 Pin 



7-40V 



200mA 



5V 



^A78S40 



MOT, NAT 



16 Pin 



2.5-40V 



1.5V 



1 .24V 



Universal subsystem IC 



125/7 



IPS. SIL 



P-P 



16 Pin 



8-35V 



100mA 



5.1V 



33060/ 
34060/ 
35060 



IPS, MOT 



14 Pin 



7-40V 



500mA 



5V 



1060 



IPS. PLES 



16 Pin 



20mA into 5V 

shunt 

regulator 



40 mA 



3.7V 



LT1070 



LT 



5 Pin 
Power 



3-40V 



5A 



1.24V 



Self-contained power 
IC. 



"Manufacturers: CS = Cherry Semiconductor, ERIC = Ericsson, EXAR = Exar. GE = GE/RCA'Harris. GS = Gold Star, IPS = Integrated Power 
Semiconductor, LT = Linear Technology, MAX = Maxim, MOT = Motorola, NAT = National Semiconductor, RAY = Raytheon, SGS = SGS-Thom- 
son, SIG = Signetics, SIL=Siliconix, SLG = Silicon General, Tl = Texas Instruments. UN! = Unitrode 



X B, 



TIMING 
L 'i v P ABMa [OR 



SYN 



TIMING 
RESISTOR 



R-C 
OSCIL- 
LATOR 



CLOCK 



J 



SOFT-START 
CAPACITOR 



I 



REGULATED 
INTERNAL 
SUPPLY 



INPUT 
^CAPACITORi 



. RAMP 



L: 



LOGIC 

AND 

orivt 
GiRcun 



i: IMi'AFiAIMR 



WIRED- OR 



VOLTAGE 
REFERENCE 

AND 
REGULATOR 



_L 



T 



ERROR 
AMP 



£* 



LI 



EXTERNAL TRANSISTORS 
\0R FETS 

SNUBBER 



L©— ' 



-OSHUT DOWN 



^ 



THRESHOLD 



CURRENT 
SENSOR 



-Wr- 




V0LTAGE FEEDBACK 



I 

I ,_. 



I 



FIG. 11— THIS "GENERIC" SLOCK DIAGRAM of a switching regulator is useful in sorting 
out the functions which make up the circuit. 



Sometimes a failure which looks 
like it might have been caused by 
output overload is actually 
caused by a low input voltage. 
When the input voltage drops, 
the regulator's duty cycle in- 
creases, raising the input cur- 
rent. The increased current may 
further drag down the voltage, re- 
sulting in even higher current 
drain, until an input fuse or cir- 
cuit breaker trips or something 
burns out. 

If the output is dead, check the 
rectifier and filter, the drive tran- 
sistors and the output trans- 
former or inductor. Before replac- 
ing damaged components check 
any snubber or surge-suppres- 
continued on page 64 






55 



O 

Z 

o 

EC 

LU 



c 
< 

IE 



Schools and colleges teach 
many things — but they 
don't teach electronic- 
equipment manufacturing. Most 
of us pick up that type of knowl- 
edge through on-the-job experi- 
ence or through our hobbies, (In 
fact, hobby magazines like Ra- 
dio-Electronics probably are the 
most common teachers of prac- 
tical design and construction.) 
However, many engineers gradu- 
ate from school and enter the 
work force with little or no prac- 
tical experience. 

Recently I had to set up a train- 
ing center to instruct young engi- 
neers at my company in basic 
manufacturing processes. My 
task was to create a small man- 
ufacturing factory where stu- 
dents would build an electronic 
product. In the process, they 
would experience every stage of 
the manufacturing process: in- 
terpreting engineering draw- 
ings, buying parts, testing them, 
building the product, and ship- 
ping it to the customer. The proj- 
ect was dubbed the Manufactur- 
ing Technology Facility (MTF). 

With a limited budget and lim- 
ited time in which to teach more 
than 400 people, I searched for 
automation aids that would 
speed up the mundane work 
without attenuating the man- 
ufacturing experience we were 
trying to impart. One area I at- 
tacked was incoming inspection. 
In a normal manufacturing 
plant, parts are bought from 
many sources. When they arrive, 
they are tested to ensure they 
work, because it can cost more 
than $10 to find and fix a bad SI 
part in a finished product. 

The product we built had more 
than thirty different types of elec- 
tronic parts, which fell into five 
groups: resistors, capacitors, di- 
odes, transistors, and IC's. What 
I needed was a low-cost way for 
students to inspect the parts 
quickly, but with minimum 
chance for error. The result was 
what we now call the Component 
Inspection System (CIS). It incor- 
porates a capacitance meter, an 
IC tester, and a computer-con- 
trolled voltmeter used for testing 
resistors and diode and tran- 
sistor junctions. The CIS soft- 
ware includes a database con- 
taining each components speci- 
fications, complete with pass/fail 
criteria. In addition, the system 



contains a data-logging function 
that allows us to maintain a rec- 
ord of each vendor's quality histo- 
ry which is useful in selecting 
vendors. 

In future articles, we will de- 
scribe different components of 
the CIS hardware and software. 
This time we'll present a $15 two- 
IC circuit that lets you use your 
PC as a capacitance meter. Later 
installments will include com- 
plete details for building sophis- 
ticated component and IC test- 
ers. When space is available, we'll 
provide the software listings (all 
of which are in QuickBASIC): 
compiled programs and source 
code are also available. 

PC-based capacitance meter 

The first project is a capaci- 
tance meter. It will be incorpo- 
rated into the next project, a 
combined voltmeter, ohmmeter, 
and capacitance meter on a PC 
board, but it can also be used as a 
stand-alone test instrument. 
First let's discuss the details of 
hardware operation. 

The circuit, shown in Fig. 1. 
consists of two ICs: a 555 timer 
(IC1) and a quad bilateral switch 
(IC2). The 555 is the heart of the 
circuit. When configured in the 
astable (one-shot) mode, the 
length of the pulse generated at 
pin 3 is directly proportional to 
the value of the timing resistor 
(Rl) and the timing capacitor 
(C x ). With a fixed timing resistor, 
the duration of the output pulse 
will be directly proportional to 
the value of the timing capacitor. 
Thus, by connecting a known re- 
sistor and an unknown capacitor 
to IC1, triggering it, and then 
measuring the length of the re- 
sultant output pulse, we can cal- 
culate the value of the capacitor. 

We wanted to obtain an effec- 
tive meter range of 20 pF to 20 ji.F. 
To achieve such a wide range, we 
had to use two different timing 
resistors — and that's where Ihe 
4066 comes in. By driving pin 12 
of IC2 high, the IC effectively par- 
allels a second resistor (R2) with 
the main timing resistor (Rl). 
Doing so makes it easier to mea- 
sure large- value capacitors. With 
R2 switched in, the effective 
range of the meter is 0.1 ^F to 20 
H,E If the value of the unknown 
capacitor is less than 0.1 fxF, R2 
can be switched out of the circuit 
(automatically by the software) 




and the capacitor can then be re- 
measured. 

The PC connection 

The capacitance meter at- 
taches to your PC via three lines 
(plus ground) of a standard par- 
allel port. The autofd signal con- 
nects to ICl's trigger input (pin 
2) to initiate the timing cycle. The 
ack line from the port connects to 
ICl's output (pin 3). fn operation, 
our software drives autofd 
momentarily low and then high 
again to trigger IC1. While the PC 
counts the time interval, the ca- 
pacitor charges until ICl's inter- 
nal comparator drives its output 
from low to high. At that time, 
ack senses the end of the timing 
cycle and alerts the PC to stop 
counting. The software then con- 
verts the elapsed time interval to 
a capacitance value. 

The ds line from the parallel 
port drives the bilateral switch. 
Initially, the switch is on. which 
places R2 in parallel with Rl, and 
allows you to measure the high 
range (0.1-20 \iF). If the resul- 
tant count is less than a specified 
value, the software switches R2 
out of the circuit, obtains a new 
count, and then scales it for the 
low range (20 pF-O.lfxF). 

Because the software depends 
on a timing loop, it must be cali- 
brated before use. Calibration 
consists of making two readings: 
one accounts for stray circuit ca- 
pacitance; the other involves 
measuring a known capacitor to 
provide a standard. The circuit 



56 



EXPERIMENTING WITH 

PC-BASED 
TEST EQUIPMENT 




must be recalibrated if the PC's 
operating speed changes (e.g.. 
via a turbo mode), or if you con- 
nect the meter to another PC. 

Software 

The simplicity of the hardware 
is made possible by the software. 
Although we won't discuss all the 
details here, there are a few 
points you should be aware of in 
the event you wish to modify the 
software. First, there are two pro- 
grams. CAP and CAPFAX; CAP is 
the main program and CAPFAX 
helps calibrate the software. 
Both programs are written in Mi- 
crosoft's QuickBASIC. The soft- 
ware must be compiled; inter- 
preters (including BASICA and 
GWBAS1C) do not run quickly 
enough to measure capacitors 
less than 1 |j,F If you want to use 
the software as is, you don't need 
to own a copy of QuickBASIC ; a 
compiled version is available 
from the author, as mentioned in 
the parts list. However, to modify 
the software, you will need a copy 
of QuickBASIC. 

Now let's talk about CAR Before 
doing anything else, the software 
locates the I/O address of your 



parallel printer port. That is nec- 



essary because some cards don't 
address their printer ports at the 
standard location (0378h or 888 
decimal). In Listing 1, line 16 lo- 
cates the address and stores it in 
variable C. (Note that line num- 
bers are optional in QuickBASIC; 
they are shown here for reference 
only.) Variables B and A, which 
are derived from C, are used to 
read ICl's output and to operate 
IC2, respectively. 

The measuring function be- 
gins in line 18, which switches in 
the 100K resistor. The next line 
initializes the counting variable, 
X. The next line contains two 
functions. The first, consisting 
of the OUT statements, generates 
a negative-going pulse to trigger 
IC1. The WHILE/WEND loop then 
continually increments X until 
pin 3 of IC1 goes low. 

The remainder of the program 
determines if R2 should be 
switched in, converts the count 
to a capacitance value, and dis- 
plays the value in an appropriate 
form (pF or yiF). 



Build your own 

low-cost PC-based 

test equipment 

JAMES J. BARBARELLO 




You use the second program, 
CAPFAX, to create a data file (CA- 
PFAX. DAT) that contains infor- 
mation required by CAP. (CAP- 
FAX is shown in Listing 2.) Five 
values are required: zero offset, 
low factor, high factor, picofarad 
limit, and microfarad limit. Zero 
offset is the count obtained with 
no capacitor connected to the cir- 
cuit. In operation, CAP subtracts 
this value from the count ob- 



> 

-< 

(0 



57 





+5Vi 






!, ; 


►10MIG 


14 


R2 < 
1G0K> 


1 

2 
3 


IC1 
555 


1, 

6 ( 




1 
4. 

5 

7 


IC2 

4056 


13 
12 


iVtj 
10 

T 








Cv3 








^ 




SEE - 
TEXT 




4. 












P1 

TQ 

EBINJEB 




14 


10 






Gl 


ID, 


> 


"•ACK « 


i nfi 




AUTOFD 




tOBI Jjg 





LISTING 1 



FIG. 1— SCHEMATIC DIAGRAM. The ca- 
pacitance meter consists of two IC's: a 555 
running in the astable mode, and an ana- 
log switch that allows the software to per- 
form automatic range switching. 



tained during measurement to 
eliminate the effects of stray cir- 
cuit capacitance. Low factor and 
high factor are reference values 
that tell CAP what the count 
should be for a 0.100 u.F capaci- 
tor in the low and high ranges. 
Using those factors, CAP calcu- 
lates the value of the unknown 
capacitor. Picofarad limit and mi- 
crofarad limit are values that CAP 
uses to determine when to switch 
ranges, and how to format the 
measured value for presentation 
on the screen. CAPFAX is used 
during calibration, and any time 
you change the circuit layout, PC 
operating speed, or the PC itself. 

Construction 

The circuit's simplicity allows 
just about any construction 
method to be used. The easiest 
approach is to use a solderless 
breadboard. You'll also need a 
source of 5-volt DC power; in a 
pinch you could power the circuit 
with three batteries in series ( the 
4.5 volts produced should be ade- 
quate to generate the required 
TTL logic levels.) If you use a 
CMOS 555, the batteries will last 
a long time. 

As shown in Fig. 1, several pins 
of IC2 must be grounded to en- 
sure proper switching operation. 
If those pins are not grounded, 
the meter may operate erratically. 

To connect the unknown ca- 
pacitor, you could insert it di- 
rectly into the solderless bread- 
board. For more convenient 



i 

2 

3 
4 

5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
IS 
19 
20 
21 
22 
23 
24 
25 
26 
27 
23 
29 
30 
31 
32 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
44 
45 
46 
47 
48 
49 
50 
51 
52 
53 
54 
55 
56 
57 
58 
59 
60 
61 
62 
63 
64 
65 
66 
67 
68 
63 
70 
71 
72 
73 
74 
75 
76 
77 
78 






R EM ******************* »***. 
REM** CAP.BAS * 

REM** V300114 * 

IgV* **************** A ***** * 

REM 

REM** NOTE: THIS PROGRAM MUST BE COMPLIED WITH QUICKBASIC 4,0 PRIOR TO 
USE 
REM 

DEF SEG = 64: DEFINT A-C, I, K: DEFLNG X 
OPEN "r", 1, "capfax.dat", 50 

FIELD 1, 10 AS ol$, 10 AS fl$, 10 AS fh$, 10 AS pf$, 10 AS ufS 
GET 1, 1 

offsetlo = VAL(olS) : FACTOHLO! = VAL{fl$): FACTORHI ! = VAL(fh$) 
apf = VAL(pf$): auf - VAL(ufS) 
CLOSE 

FACTQRLOPF* = FACTOHLOI / 1000000: factorhipf # = FACTORHI! / 1O00000 
GOSUB SI: C = PEEX{8) + 256 * (PEEK(9) ) +2: B-C-l: A=B-1 
RESTART: 
OUT A, 64 

X » 0: LOCATE 12, 31: PRINT " MEASURING... " ,- 
OUT C, 2: OUT C, 0: WHILE (INP(B) AND 64): X - X + 1: WEND 
SELECT CASE X 
CASE IS > auf 
measuredvalue - X / 

LOCATE 12, 31: 

LOCATE 24, I: 

LOCATE 12, 36: 

SOTO SKIPTT 
CASE ELSE 

OUT A, 
END SELECT 
OUT C, 2: X = o: 
SELECT CASE X 
CASE IS > apf 

measuredvalue 

measuredval ue 

LOCATE 12, 31: 

LOCATE 24, 1: 

LOCATE 12, 36: 

GOTO SKI PIT 
CASE ELSE 

AA = 0: XX = 
REDO: 

OUT C, 2: X = 0: OUT C, 0: WHILE (INF(B) AND 64) 

IF AA < 5 THEN AA = AA + 1: XX » X -t XX: FOR i = 
GOTO REDO 

mean = XX / 5: X - mean 

LOCATE 12, 31: PRINT SPACES(18); 

measuredvalue = (X - offsetlo) / FACTORLOPFJ 

LOCATE 24, 1: PRINT "Lo - pf" ; 

LOCATE 12, 36: PRINT USING "♦### pf " r measuredvalue 
END SELECT 
SKIPIT: 

LOCATE 24, 62: PRINT SPACESU7); 
COLOR 7, 0: LOCATE 20, 29 
COLOR O, 7: PRINT " n "; : COLOR 7, 
COLOR 0, 7: PRINT " E " ; : COLOR 7, 
Tryagain: 

ReplyS = UCASES (INPUTS (1)) 
SELECT CASE ReplyS 
CASE "M" 

LOCATE 12, 37: PRINT SPACES (6) 
GOTO RESTART 
CASE "E" 

CLOSE : END 
CASE ELSE 

BEEP: GOTO Tryagain 
END SELECT 
END 
SI: 

CLS : LOCATE 3, 23: COLOR 0, 7: PRINT SPACES (35) 
LOCATE 4, 23: PRINT " PC CAPACITANCE METER " 
LOCATE 5, 23: PRINT '• (c) 1990, JJ BARBARELLO " 
LOCATE 6, 23: PRINT SPACE$(35)s COLOR 7, 

LOCATE 11, 30: PRINT CHRS(222) ; STRINGS(19, 223); CHRS(221) 
LOCATE 12, 30: PRINT CHR$(222): LOCATE 12, 50: PRINT CHK$(221) 
LOCATE 13, 30: PRINT CHR$(222); STRING$(19, 220); CHR$(221) 
RETURN 



FACTORHI ! 
PRINT SPACES (18) ; 
PRINT "Hi - uf " ; 
PRINT USING "iitf.t uf"; measuredvalue 



OUT C, 0: WHILE (INP(B) AND 64): X = X + 1: WEND 



- (X - offsetlo) / FACTORLOl 

= INT [measuredvalue * 10000) / 10000 

PRINT SPACES (18) ; 
PRINT "Lo - (if; 

PRINT USING "*.,## uf"; measuredvalue 



X = X + It WEND 
1 TO 100: NEXT i: 



LOCATE 24, 62: PRINT "Count:"; 

O: PRINT "easure, or " : 
O: PRINT "nd ... "; 



access, you could use a pair of 
binding posts connected via 
short lengths of wire. Although 
doing so adds stray capacitance 
to the circuit, it can be canceled 
during calibration. 

After building the circuit, wire 
a short cable from a standard 
DB-25 male connector and four 



lengths of wire. Connect the ap- 
propriate pins on the connector 
to the circuit, and the DB-25 end 
to your PC's parallel port. 

Calibration 

Calibration must be performed 
prior to using the meter. To per- 
form the calibration, you need a 



58 



LISTING 2 






PARTS LIST 



1 


REM** CAPFAX. BAS 




2 


REM** REVISE CAPFAX.DAT EHTRIES 




3 


REM** V900114 




4 


CLS : OPEN "r", 1, "capfax.dat", 50 




5 


FIELD 1, 10 AS zero?, 10 AS low$, 10 AS highS, 


10 AS pf$, 10 AS 


6 


GET 1, 1 




7 


LOCATE 1, 30: PRINT "REVISE CAPFAX.DAT FILE" 




3 


LOCATE 3, 1: PRINT "Zero Offset: •< ; zeroS 




9 


LOCATE 4, l: PRINT "Low Factor : "; lowS 




10 


LOCATE 5, 1: PRINT "High Factor: "; higtvS 




11 


LOCATE 6, 1: PRINT "pF Limit ; " ; pfS 




12 


LOCATE 7, l: PRINT "up Limit : "; uf$ 




13 


LOCATE 9, 10: PRINT "Change [Y/H) ? "; 




14 


GOSUB yesno: IF a$ = "N" THEM GOTO endit 




15 


z$ - iero$: 1$ = low?: h$ - high?: p$ = pf$; US 


= ufS 


16 


getnewones : 




1? 


VIEW PRINT 3 TO 23: CLS : VTEW PRINT 




IS 


LOCATE 3, 1: PRINT "Zero Offset; " ,- z$ 




19 


LOCATE 4, 1: PRINT "Low Factor : '•'; IS 




20 


LOCATE 5, 1: PRINT "High Factor: "; h$ 




21 


LOCATE 6, I: PRINT "pF Limit : " ; pS 




22 


LOCATE 7, 1: PRINT "uF Limit : "; Q$ 




23 


LOCATE 9, 10: LINE INPUT "New Zero Offset..."; 


:S 


24 


IF z$ = "" THEN zS = zeroS ELSE LSET zeroS = zS 


-1 U " 


25 


LOCATE 9, 28: PRINT zS 




26 


LOCATE 10, 10: LINE INPUT "New Low Factor..."; 


1$ 


27 


IP IS = "" THEN IS = lowS ELSE LSET lowS = IS + 


II 11 


28 


LOCATE 10, 27; PRINT IS 




29 


LOCATE 11, 10: LINE INPUT "New High Factor..."; 


hS 


30 


IF hS = "" THEN hS - fsighS ELSE LSET highS =- hS 


t 5 « 


31 


LOCATE 11, 28: PRINT h$ 




32 


LOCATE 12, 10: LINE INPUT "New pF Limit "; 


PS 


33 


IF pS = "" THEN pS = pfS ELSE LSET pfS = pS + " 


11 


34 


LOCATE 12, 28: PRINT pS 




35 


LOCATE 13, 10: LINE INPUT "New uF Limit "; 


u$ 


36 


IF u$ = "" THEN US - ufS ELSE LSET ufS = uS + " 


ii 


37 


LOCATE 13, 28: PRINT u$ 




38 


LOCATE 15, 10: PRINT "Change (Y/N)?"; 




39 


GOSUB yesno: IF a$ = "N" THEN GOTO endit ELSE GOTO getnewones 


40 


endit: 




41 


VIEW PRINT 3 TO 23: CLS : VIEW PRINT 




42 


LOCATE 3, l: PRINT "Zero Offset: "; zero? 




43 


LOCATE +, is PRINT "Low Factor : "; low$ 




44 


LOCATE 5, l: PRINT "High Factor: "; highs 




45 


LOCATE 6, 1: PRINT "pF Limit : "; pfS 




46 


locate 7, 1: PRINT "uF Limit : "; ufS 




47 


LOCATE 15, 10: PRINT "Save (Y/N)? " ; 




43 


GOSUB yesno: IF aS = "N" THEN CLOSE : PRINT "NO 


SAVE": LOCATE IS 


49 


END 




50 


PUT 1, 1: CLOSE : PRINT "New Data Saved.": LOCATE 18, 1: END 


51 


yesno: 




52 


aS - UCASES( INPUTS (1)) 




53 


SELECT CASE a$ 




54 


CASE "Y" 




55 


RETURN 




56 


CASE "N" 




57 


RETURN 




58 


CASE ELSE 




59 


GOTO yesno : 




60 


END SELECT 





ufS 



REUISE CAPFAX.DAT FILE 



lero Offset: 75 

.□u Factor : 2195000 

Ugh Factor: 25000 

)F Linit ! 1000 

iF Limit : 10000 

Change (Mi)? 



FIG. 2 — CAPFAX.EXE calibrates and sets the range-switching values for the main pro- 
gram, CAP.EXE. 



0.1 |xF capacitor for which you 
know the exact value. If you don't 
have one, use a capacitor marked 
0.1 ixFwith the best tolerance you 
can find (at least 5% or 10%). 



Begin by executing CAP- 
FAX.EXE; you'll see a screen like 
that shown in Fig. 2, except that 
the five values will all be 0.0. To 
change values, press Y, and then 



All resistors are 'A-watt, 5%, un- 
less otherwise noted. 

R1 — 10 megohms 

R2— 100,000 ohms 

Semiconductors 

IC1— 555 timer 

tC2-^tQ66 quad bilateral switch 

Other components 

P1 — 25-pin male D connector 

Miscellaneous: 0.1 uF high-toler- 
ance capacitor for calibration, sol- 
derless breadboard, five-volt power 
source, wire, solder, etc. 

Note: The following is available 
from J J Barbarello, RD#3, Box 
241 H, Tennent Road, Manalapan. 
NJ 07726: Compiled version of 
the software (CAP and CAPFAX), 
with datalogging, on 5%-inch 
double-density PC diskette, 
$8.00. The author will be happy 
to answer any questions. Please 
include a self-addressed stamp- 
ed envelope tor reply. 



enter the following values as a 
starting point. 

• Zero Offset: 

• Low Factor : 1 

• High Factor: 1 

• pF Limit : 1000 

• U.F Limit : 10000 

After entering those values, re- 
spond by pressing N (No) to the 
Change question. Respond Y 
(Yes) to the Save question to 
create the initial CAPFAX.DAT 
file. 

Now connect the circuit to your 
PC's printer port, but make sure 
there is no capacitor connected 
to the test points. Apply power to 
the circuit and start the software 
by typing the command CAP at 
the DOS prompt. 

The screen will display some 
value of capacitance, and a count 
in the lower right hand corner. 
Press M to measure again. Dis- 
regard the value displayed, but 
note the count, which should be 
between 5 and 100, depending on 
your particular PC and circuit 
construction). That value is the 
zero offset. 

Next connect the known 0. 1 p.F 
capacitor and press M to mea- 
sure. Again, disregard the value 
displayed, but note the count. 
Multiply that number by 10 to ob- 
tain the low factor. For example, if 
the count is 123456, the low fac- 
tor is 1234560. Leave the 0.1 u,F 
capacitor in the circuit. 

Execute CAPFAX again and en- 



s 

5 



55 



ter the appropriate values into 
the Zero Offset and Low Factor 
fields. Also, change the u.F limit 
to 1. Save the new data and re- 
execute CAP Press M to measure. 
Disregard the value, but note the 
count, and multiply it by 10 to 
obtain the high factor. For exam- 
ple, if the count is 1234, the high 
factor is 12340. Execute CAPFAX 
one more time to enter the high 
factor and change the u,F limit 
back to 10000. Save the revised 
data. 

Use 

Using the PC-based capaci- 
tance meter is straightforward. 
With your PC on and the meter 
connected to the printer port, ap- 
ply power to the meter. At the 
DOS prompt, type CAP and press 
Enter. Insert the capacitor to be 
measured, and press M. The val- 
ue appears in the middle of the 
screen, and the bottom indicates 
the range (pF, p.F low, |iF high}, 
along with the timer count. To 
end the program, press E. 

The (xF limit and pF limit fac- 
tors are used to determine how to 
format the measured value. If you 
measure a capacitor that dis- 
plays 0.00 \iF, but has a count 
greater than 0, you are in a "no- 
man's land" between the two lim- 
its. Execute CAPFAX and in- 
crease the pF limit factor. Doing 
so increases the pF formatting 
range and allows the measured 
value to be displayed properly. 

Remember that if you vary the 
meter circuit or your PC, you 
should recalibrate the software to 
maintain accuracy. 

Next Time 

In the near future we'll incor- 
porate the capacitance-measure- 
ment circuitry into a combina- 
tion instrument that measures 
resistance, capacitance, and volt- 
age. The device allows you to 
measure resistors, capacitors, 
diodes, and transistors. Because 
it is computer controlled, it can 
be the heart of an automated in- 
spection system for your shop or 
business. You can save a lot of 
troubleshooting time by ensur- 
ing that the IC's you plan to use in 
a project function properly before 
you use them. The last project in 
this series is an IC tester that al- 
lows you to verify operation of 
most 14- and 16-pin TTL and 
CMOS IC's. R-E 



DRAM TESTER 



continued from page 40 



to operate a few minutes for max- 
imum stability, set R5 at 100 ns 
on the dial, and adjust R19 for a 

J 



low clock pulse of 200 ns. Mea- 
sure the pulse at the 1.0-volt DC 
level. Next turn R5 fully counter- 
clockwise; the low clock pulse 
should be 150 ns. Turn R5 fully 
clockwise; the low clock pulse 
should be 300 ns — if not, adjust 
R17 for the proper "dial spread." 




FIG. 9— PARTS-PLACEMENT DIAGRAM. The parts shown in color are installed on the 
"bottom," or solder side of the board — that is, the side opposite that with the Zl F sockets. 



The R17 and R19 adjustments 
will interact somewhat, so adjust 
by small increments, and again 
calibrate R19 at the 100-ns dial 
setting with R5 after each change 
to R17. This adjustment should 
be easy; both potentiometers 
should end up somewhere near 
midrange. 

If you do not have a scope im- 
mediately available to calibrate 
the access-time control, set R17 
and R19 to midrange, which 
should be near calibration, and 
use the speed test for a relative 
indication; the function and volt- 
age margin tests should work 
fine. All you have to do now is 
install the unit in an appropriate 
case and put it to good use. R-E 




FIG. 10— THE FINISHED BOARD is neat 
and compact — and, of course, quite 
useful. 



60 



ROGER P. NEWELL* 



A NEW ERA OF PERSONAL COMMUNI- 

cations may be just over the hori- 
zon. Imagine the freedom and 
mobility of making and receiving 
calls away from your desk and 
home — In the street, roaming 
around your office, or even on the 
golf course. This new service will 
be provided by Personal Commu- 
nications Networks (PCN's), 
which are radio-telephone net- 
works designed to run parallel to. 
and compete with, the Public 
Switched Telephone Network 
(PSTN) that we are all familiar 
with. 

PCN's are intended to provide 
mobile telephone service with 
quality and reliability equivalent 
to wireline. The handset is a dig- 
ital radio designed to permit pri- 
vacy and security that meet the 
standards of a fixed network, 
with usage rates that are com- 
parable, or only slighdy higher, 
than those charged by wireline 
services. Those advantages can 
come only if there is a large 
number of subscribers. A further 
objective of PCN's is to make effi- 
cient use of the radio spectrum in 
order to have as large a capacity 
as possible. 

What is a PCN? 

A generally accepted definition 
of a PCN is that it is a complete 
telephone system, running paral- 
lel to (and competing with) the 
traditional fixed telephone sys- 
tem. A PCN consists of pocket ra- 
dio telephones communicating 
with fixed base stations in the 
street or in buildings. PCN's will 
permit any person to make or re- 
ceive telephone calls, no matter 
where he or she might be — at 
home, on the street, or in the of- 
fice. Using digital radio tech- 
niques in combination with a 
low-cost pocket-sized handset, 
the PCN will provide a fully 
mobile service with enhanced 
quality and all the features and 
functions of a standard tele- 
phone system. The underlying 
idea is that calls should be made 
to a person, not a place. By as- 
signing a personal telephone 
number to an individual (rather 

•Roger P. Newell is a telecommunications attorney 
practicing in New York City. He is also editor of 
Microcell Report, a monthly newsletter on microcell 
technology. 



Personal 

Communication 

M ETWO R KS 



Can microcell technology of PCN's 

make mobile communications truly 

affordable for everyone? 



than a line from the phone com- 
pany's central office] the PCN will 
be able to ensure that the cus- 
tomer is always able to be 
reached in an instant. 

A more basic system, called 
Telepoint, operates as a radio 
pocket payphone, allowing calls 
to be placed whenever the user is 
within radio range of a base sta- 
tion installed by the Telepoint op- 
erator. When a subscriber wants 
to make a call, he or she goes 
within radio range of a public 
base station installed by the Tele- 
point operator, opens the hand- 
set and punches in a personal 
identification number (PIN). The 
base station will validate the PIN, 
and accept the dial information. 
The call is then extended through 
the public telephone network. 
The base station collects infor- 
mation on the caller's identity 
(transmitted by the handset) and 
the duration and distance of the 
call. The Telepoint company will 
send a bill to the customer for all 
calls that happen to have been 
made during the month. 

Market demand 

The desire for communica- 
tions mobility is strong, A.D. Lit- 
tle, a respected marketing con- 
sultant firm, has done market re- 
search that indicates that a large 
fraction of the nation's house- 
holds would gladly subscribe to a 
PCN. Although market demand 
depended on the price of the 



handset and the monthly 
charges for the service, 40% of all 
households surveyed were likely 
to subscribe to PCN's, assuming 
monthly service charges of $10 
per month over the consumer's 
current telephone bill, and a 
handset price of $100. When the 
service premium increased to 
$40 per month, and handset 
prices to $250, 14% of all house- 
holds indicated the willingness 
to buy PCN service — and that's 
only the residential market. Be- 
tween 25 and 35% of all busi- 
nesses were likely to subscribe to 
PCN's. 

A.D. Litde concluded that the 
interest in PCN's is nearly double 
that of most other new services. 
It also found that annual reve- 
nues from personal communica- 
tions will range from $10 billion 
in the first year or two to over $30 
billion as the service matures. 
That's enough to make even a 
telephone company's mouth 
water, and explains the current 
high interest in personal com- 
munication networks. 

How it works 

In some ways PCN's are similar 
to cellular telephones. In each 
case, the radio telephone trans- 
mits signals to a fixed base sta- 
tion, which then connects the 
call to another subscriber, or the s 
public-switched telephone net- ^ 
work. The fundamental dif- £ 
ference is that PCN's use ex- 2 



61 



w 

D 

z 
O 
c 
h- 
O 



tremely low power for the radio 
link between the handset and the 
base station — about 10 milliwat- 
ts peak power compared with 
600 milliwatts for cellular porta- 
bles, and 3 watts for a car tele- 
phone. Low power means short 
range, which would seem to be a 
severe drawback for a radio tele- 
phone, but is actually the reason 
for the current intense interest in 
PCN's, With a short range, it is 
necessary to have very large num- 
bers of base stations, each cover- 
ing a microcell whose radius is 
from 200 meters to perhaps half 
a kilometer. In comparison, cel- 
lular cells are usually several 
miles wide. 

Since the spectrum can be re- 
used in each of those microcells. 
PCN's are more spectrum effi- 
cient than cellular phones, and 
can provide service to many more 
people. With such a large capaci- 
ty, the investment cost per sub- 
scriber can be kept extremely low. 
The initial cost of a PCN is ex- 
pected to be about $300 per sub- 
scriber, compared with $800 for 
cellular and $1,600 for wireline 
networks. 

In addition, the use of low 
power also brings manufactur- 
ing advantages into play. If the 
handsets broadcast at low power, 
less power is needed in the bat- 
tery which means smaller bat- 
teries, and therefore, smaller 
terminals and micro-mini- 
aturized components are used. 
All that translates into longer talk 
time, with lower prices available 
to the public. 

Spectrum scarcity 

Microcell technology has the 
potential to change the way we 
communicate, and to be a pro- 
digious revenue-producer for 
those supplying the equipment 
and service. Yet PCN's are not 
springing up all over the land- 
scape. The reason is that an es- 
sential element is in short 
supply — the radio spectrum for 
handset-to-base transmissions. 
Virtually all of the technically ap- 
propriate spectrum has been al- 
located to users who guard it 
with the intensity of a bear pro- 
tecting her cubs. The Federal 
Communications Commission 
(FCC} and industry are attempt- 
ing to find a path through the 
spectrum thicket. The FCC 
could, in theory, clear spectrum 



for a PCN service simply by real- 
locating a slice away from current 
users; but past experience has 
shown that trying to remove a 
slice of the spectrum is like walk- 
ing into a buzzsaw. 

As an alternative, spectrum 
could be assigned to PCN on a co- 
primary (sharing) basis, or on a 
secondary basis, requiring PCN 
operators to defer to the primary 
users of the spectrum. But shar- 
ing leaves the operators unsure 
of whether their spectrum is suf- 
ficiently solid to warrant the high 
investments needed to set up 
their systems. Either method 
would involve bloody battles in 
the halls of the FCC between the 
spectrum haves and have-nots, 
and would take several years to 
resolve. 

So companies throughout the 
telecommunications industry 
are exploring ways to bring to 
consumers the benefits of low- 
cost mobile phones, despite the 
shortage of frequencies. Over 50 
applications for experimental li- 
censes for PCN's and Telepoints 
have been filed in the U.S., and 13 
in Canada, seeking to test a vari- 
ety of technologies. For example, 
one company which owns a net- 
work of interbuilding microwave 
systems in New York City, will test 
its use as the backbone distribu- 
tion network for a PCN. Many ap- 
plicants, especially the Bell 



Operating Companies, plan to 
hedge their bets by testing every- 
thing in sight. At this time, most 
of the testers are still in the pre- 
paratory stage, and that is the 
reason why few results have been 
publicly reported. 

CT2 systems 

One system, called Cordless 
Telecommunications, 2nd Gener- 
ation (CT2), is drawing interest 
because it uses comparatively lit- 
tle spectrum. It can be used for 
Telepoint, residential cordless 
phones, and wireless PBX's for 
use in offices. The technique 
uses frequency-division multiple 
access (FDMA) to divide four 
megahertz of spectrum into 40 
channels of 100 kilohertz each. 
The handset checks each of the 
40 channels at 750 millisecond 
intervals, and if it finds another 
channel with less interference, it 
will switch to the new channel. 
When used for residential cor- 
dless telephones, CT2 has mar- 
keting advantages over current 
analog cordless telephones, since 
CT2 telephones tend to be small- 
er, have a greater range, and are 
more difficult to be overheard by 
one's neighbors. 

CT2 operates in the 800-1000 
MHz range, but only three mega- 
hertz of spectrum remain unas- 
signed in that range, and those 
frequencies were promised to 




INITIAL 
SIGNAL 




F1 F2 F3 H F5 



F6 F7 F8 F9 FID 



«-t 



BASEBAND °- 
SIGNAL 



MIXER 



J T 



CLOCK I- 



DIGITAL 
FREQUENCY 
SYNTHESIZER 



F3F8F5 F7 F3F8F5 F7 

HI I,t HI I . t 

RAPIDLY 

i CHANGING 

CARRIER 
FREQUENCY 
SEQUENCE 



MIXER 



L 



-O RECOVERED 
BASEBAND 
SIGNAL 



DIGITAL 
FREQUENCY 
SYNTHESIZER 



PN SEQUENCE 
GENERATOR 
(3.8.S...7..,) 



I M FREQUENCY 

INPUT 



FREQUENCY I 
INPUT 



PN SEQUENCE 
GENERATOR 
(3,8,5.7...) 



TRANSMITTER 



RECEIVER 



FIG. 1— A FREQUENCY HOPPING SYSTEM, Pseudorandom noise sequence generators 
in the transmitter and receiver are used to output the same frequency-hopping sequence. 



62 



other mobile phone users. An as- 
signment to a Telepoint service 
would, however, run into intense 
opposition from companies al- 
ready in the market that had 
hoped to use the spectrum for 
other mobile uses. 

CT2 plus 

Another possibility lies in the 
use of a more spectrum efficient 
version of CT. Northern Telecom 
has proposed that the 3-MHz 
slices in the 900-MHz band be 
used for control channels, while 
actual communication will take 
place over a 30-MHz band, oc- 
cupying parts of the spectrum 
not being used by point-to-point 
microwave operators in any par- 
ticular location. Interference 
with microwave operators would 
be avoided by use of "smart" base 
stations which would have the 
ability to sense which frequen- 



S(I) 



cies are being used by microwave 
channels and would block those 
frequencies off from the hand- 
sets. 

The FCCs Chief Engineer, Dr. 
Thomas Stanley, presented the 
possibility that the 4 MHz being 
considered for allocation to the 
air/ground telephone service 
could be shared by microcell 
users. That may be feasible since 
the air/ground use is not likely to 
be heavy in any one location at 
any given time. 

Cellular frequencies 

Dr. Stanley also pointed out 
that under a recent FCC order, 
cellular operators are free to use 
their allotted spectrum for auxili- 
ary services, providing the pri- 
mary service of cellular telephony 
is not affected. Up to 50 MHz of 
cellular spectrum could be used 
for a PCN-type service, assuming 



I i I I 1 I I i I I i I I I i I I i „ 

a 



1 - 



m 



J l 



V 

1 

gfH + nftl 


I 




I 1 t 




1 




1 1 










1 


l ^ j 





u 








c 



















FIG. 2— SPREAD-SPECTRUM SIGNAL. The carrier signal (a) is modulated by a noise 
signal (b), resulting in a summed signal, with an expanded bandwidth. 



DATA 
INPUT 





-(XlMIXER MIXER<X)— <> 



MATCHED 
FILTER 2 



O 

CARRIER 

INPUT 



V 






FIG. 3 — DIRECT SEQUENCE uses multiple matched filters to reduce noise and increase 
successful correlation between the receiver and transmitter. Decision logic selects the 
filter output that is most likely to be correct. 



that a cellular operator would 
take precious spectrum away 
from the higher-priced cellular 
services. The hitch is that fre- 
quencies used for PCN's would 
have to be taken away from the 
profitable cellular service. Never- 
theless, NYNEX has announced 
that it would use a portion of its 
cellular frequencies to build 
PCN's in New York and Boston, 
and is expected to be operational 
by 1992. 

Spread spectrum 

Vast numbers of radio devices 
operate today with no license at 
all under the FCCs Part 15 reg- 
ulations for low-powered devices, 
including such things as garage- 
door openers and existing analog 
cordless telephones. A personal 
communications system operat- 
ing at 1 milliwatts or less of radi- 
ated power would fall under the 
power limitations of Part 15, and 
would be allowed to operate at 
any frequency, but would have to 
accept interference from existing 
and future licensed operations, 
as well as any other Part 15 de- 
vices. That's a very uncertain 
foundation for a large invest- 
ment. 

One potential solution is to 
share spectrum through "spread- 
spectrum" technology. Several 
experimental PCN's have been set 
up to explore that option, includ- 
ing PCN's to be built in Houston 
and New Orleans by a subsidiary 
of Millicom, Inc. If successful, 
they will pave the way to establish 
a personal communications ser- 
vice despite the frequency 
crunch. Results are expected by 
the end of 1991. Although spread 
spectrum has been criticized as 
expensive, and untried in public 
telephony, it may offer the only 
hope in the U.S. of getting a PCN 
service off the ground. 

Spread-spectrum modulation 
was originally developed by the 
military to permit jam-proof and 
undetectable radio communica- 
tions. Those are the qualities 
that permit low-power radio links 
without interference to or from 
other radio transmissions. By 
spreading signal strength over a 
wide bandwidth, the energy 
transmitted at any one frequency 
in the band is low. which effec- g 
tively reduces the chance of 5 
harmful interference. ^ 

Using spread-spectrum tech- 2 



63 



DISCOVER 

EXPERIMENT 

LEARN 

ADVANCE 

ELECTRONICS 

LASERS 

CAD-CAM 
HOME STUDY 

HEATHKIT 
HOMEWORKS! 

Now you can learn beginning to 

advanced electronics at home, with the 

same courses used today in the world's 

top colleges and tech schools, and pay 

a lot less! You'll learn just what yon 

want, when you want, at your own 

pace.The complete story is in our tree 

catalog, Homeworks by Heathkit. 

Order yours today, call toll-free: 

1-800-44-HEATH 

(1-800-444-3284) 





V 




YES J Please send me a FREE copy of the 
HonieWorks by Hvatlikit Catalog. 

Send 10: Heath Company, Dept. 020-056 
Benton Harbor, Michigan 49022 

Name , 



Address 



Citv. 



Slate 
I . 

El! 210 



_Zip . 



Hull Data Systems, Inc. 



CIRCLE 193 ON FHEE INFORMATION CARD 



niques, information is transmit- 
ted over a wide bandwidth using 
a pseudorandom pattern. User- 
specific codes are transmitted by 
each sender to permit the intend- 
ed receiver to select out the rele- 
vant transmission. There are two 
primary methods that are tradi- 
tionally used to do that; they are 
frequency hopping and direct se- 
quence. 

Frequency hopping is con- 
ceptually very simple. In trans- 
mitting a traditional narrow- 
band signal, the carrier frequen- 
cy is changed, or "hopped," to 
one of a great many frequency 
slots many times per second over 
a large number of channels. The 
resulting signal has an expanded 
hopped bandwidth, which is 
often in the order of a few hun- 
dred MHz. 

The hopping pattern may seem 
to be an unpredictable sequence, 
but is actually controlled by a pre- 
determined pseudorandom noise 
(PN) generator. The PN sequence 
generator is used to determine 
the varying hop slot. The intend- 
ed receiver and the transmitter 
simultaneously hop to the same 
pattern and thus can hear one 
another. A block diagram of a typ- 
ical frequency-hopper system is 
shown in Fig. 1. 

The pseudorandom nature of 
the hops has several benefits. 
Some of those benefits include 

1. An eavesdropper will have a dif- 
ficult time listening unless he 
has the code which determines 
the hop pattern. 

2. A deliberate jammer will not 
know where to put his transmit- 
ter on the band of frequencies 
since the frequency hopper 
dodges the jammer. 

3. Multiple, uncoordinated fre- 
quency hoppers will collide only 
occasionally and therefore will 
experience only a small amount 
of interference. Therefore, as 
more and more users come on, 
the quality of the signal degrades 
slowly rather than creating a 
hard limit on the capacity of a 
network. 

Direct sequence, sometimes 
referred to as "signal shredding, " 
accomplishes the same goals, 
but uses different tactics. In the 
sophisticated technique of direct 
sequencing, the carrier (infor- 
mation) signal is digitally modu- 
lated by the noise signal. Figures 
continued on page 74 



SWITCHING SUPPLIES 



continued from page 55 



sion components. Failure of 
those will allow high voltage 
spikes, possibly destroying 
switching transistors or rectifier 
diodes. Incidentally, always use 
identical or approved replace- 
ment parts for diodes and 
switching transistors. Slow 
"garden variety" components will 
fail quickly, possibly taking other 
components with them. 

Before replacing the IC, go 
through the circuit function-by- 
function. Try to narrow the prob- 
lem to one area of the circuit and 
see if any external components 
have failed. Is the IC's internal 
regulated voltage correct? If not, 
the failure almost certainly is in 
the IC. Is the oscillator running? 
If not, check the resistor and ca- 
pacitor before replacing the IC. 
Check the soft-start capacitor 
and the external shutdown in- 
put, if your circuit has them. 
Check any compensation compo- 
nents, especially if the output is 
oscillating or unstable. 

If all of the above are working 
but the output is incorrect, the 
problem is most likely either the 
IC or the voltage feedback circuit- 
ry. A malfunctioning feedback 
circuit is always tricky to trou- 
bleshoot, especially in a device as 
complex as a switching regulator. 

The best advice is to start at the 
output and go step-by-step 
through the feedback circuit. 
The voltage dividers input-to- 
output ratio should be correct, 
even if the voltage isn't. An op- 
amp or comparator's output 
should be high if the positive in- 
put is higher than the negative 
input; otherwise, it should be 
low. (Note, though, that the IC 
connects two amplifiers and 
other circuitry together in a 
wired-OR connection. Any one of 
several problems can bring the 
error amp's output low] Check 
any feedback windings and rec- 
tifiers, optocouplers, and so on. If 
you still haven't found the prob- 
lem, replace the IC. 

Troubleshooting switching 
regulators can be tricky. Just re- 
member to go through the circuit 
step-by step, and keep the basics 
in mind when you encounter 
problems. r-e 




More on toner-cartridge reloading and Santa Claus 
machines, and some VHF and Microwave resources. 




DON LANCASTER 



Every now and then, it seems a 
good idea to go back over 
some of our older Hardware 
Hacker subjects and bring them up to 
date. Certainly one of the most popu- 
lar topics ever found on our helpline 
involves... 

Toner cartridge reloading 

PostScript and other laser printers 
are fast becoming a major industry. 
There are many millions of units now 
in use. By far the best and the most 
popular versions use several styles of 
laser engines made by Canon, These 
engines were originally intended to 
accept a throwaway plug-in cartridge. 
Inside the cartridge is a source of 
toner, a photosensitive drum, and a 
spent-toner holding tank. 

Played according to the rules, you 
buy these cartridges for $120, use 
them for 4000 copies, and end up 
with a pcr-page toner cost of three 
cents. 

As we have seen before, you can 
easily reload these cartridges your- 
self dozens of times. Today, you can 
do so in two minutes for a cost of 
$6.50 or less, and can easily reduce 
your per-page toner costs to 0.2 
cents per page, a whopping 15:1 cost 
improvement. 

Besides saving big bucks on your 
own printer, you could also resell re- 
charged cartridges for as much as 
$15 or even $19 each, as part of an 
ongoing neighborhood service. 

There's lots of exciting new things 
happening in the toner recharging in- 
dustry, so I thought we might pick up 
some fundamentals and then bring 
you up to date on the newest and the 
best insider secrets. 

What is toner? Well, it is a mixture 
of Cusually) black stuff and hot glue. 
Specifically, toner is a fine powder 
which has very precisely controlled 
magnetic, electrostatic, thermal, and 
visual properties. Most toners are 
basically a mixture of ferric oxides, 
polyethylene, and lubricants. 

Toner starts out in the cartridge's 



fresh toner tank, A magnetized roller 
then picks up a very uniform layer of 
toner. Meanwhile, a nearby pho- 
tosensitive drum gets flooded with 
light and then electrostatically 
charged. It next gets selectively dis- 
charged by a laser beam, leaving a 
charge pattern on the drum. As the 
drum rotates, it passes very near the 
magnetic roller and the toner selec- 
tively jumps onto the drum, sticking 
by electrostatic forces only where 
you want an image. 

As your drum rotates further, it 
passes very close to a highly charged 
piece of paper, and the toner particles 
then jump onto the paper. Any re- 
maining toner that was left on the 
drum gets scraped off and routed to a 
spent-toner holding tank. The pho- 
tosensitive drum then continues on 
its way for another cycle. 

Meanwhile, you now have your im- 
age on the paper. But it is only held 
there by gravity and by rather weak 
electrostatic forces. It will easily 
smear if you touch it. The paper then 
goes on to a fusion roller assembly. 
Heat and pressure will melt the toner 
and force it into the paper, giving you 
a fairly durable final hard copy. 

One very important part of most 
fuser assemblies is the wiper pad. 
The wiper pad has a small amount of 
silicon oil on it that both lubricates 
and cleans up any remaining toner on 
the pressure rollers. Wiper pads are 
usually replaced whenever a car- 
tridge is recharged. Note that just 
washing a wiper pad is a no-no. 

Our first rule: Toners vary from ma- 
chine to machine. Most Canon laser 



NEED HELP? 



Phone or write your Hardware 
Hacker questions directly to: 

Don Lancaster 

Synergetics 

Box 809 

Thatcher, AZ 85552 

(602) 428-4073 




printers use what is known as a black 
write system, since laser diodes will 
last much longer this way On the 
other hand, all but the newest and 
most expensive copiers use a white 
write system so that light ends up as 
white and dark as black. 

Thus: Copier and Laser-Printing 
toners must NEVER be interchanged 
or substituted for each other! There 
are usually mechanical interlocks that 
prevent you from plugging a copier 
cartridge into a laser printer and vice 
versa. If you attempt to defeat those 
interlocks, you will end up using the 
wrong toner. At the very least, that 
gives you useless copies, and at 
worst, it can cause serious damage. 

Similarly, toner chemistry varies 
from printer to printer, especially be- 
tween manufacturers. Our second 
rule: The refill toner you use must be 
pretested in and rated for the exact 
cartridge you are refilling. 

So where do you get refill toner and 
the wiper pads? My two favorite 
sources are Don Thompson and 
Lazer Products. There is also one 
outfit called Black Lightning that 
stocks specialty toners for T-shirt and 
fabric printing uses. 

The toner industry has its own 
trade journal, it is called Recharger, 
and is chock full of supplier ads and 
useful industry info. There are also at 
least a dozen recharging associa- 
tions who do have lots of seminars 
and conventions. Details on those 
usually appear in Recharger. 

The big news today in toner refilling 
involves new third- party hard coated 
drums. For some reason or another, 
the factory stock drums are made 
needlessly soft. The third-party 
drums instead are ultra-hard and can 
easily be used for dozens of reloads. 
One leading importer of hard drums 
is CopyMate Products. 

Let's look at some specific refilling 
details. Certainly the most popular . 
cartridges are those used in the 5 
Canon CX, SX, and LX engines. Fig- - 
ure 1 lists many popular laser printers 5 




HP MANUAL 



HP PRINTER 



02686-90920 
{CX Engine) 



LaserJet I 



LaserWriter 
LaserWriter Plus 



PS800 



33449-90906 
(SX Engine) 



LaserJet II LaserWriter NT PS810 & Turbo 

LaserJet III LaserWriter NTX PS820 & Turbo 



33459-90906 
(SX Engine) 



LaserJet IID 
LaserJet HID 



33471-90904 
(LX Engine) 



LaserJet IIP 






Personal LW 




FtG. 1— HERE'S A LIST of all the most popular PostScript laser printers, their equivalent 
service manuals, and the style of toner cartridges they use. 



and the specific engine used in each 
one. Figure 1 also reveals to you the 
outstanding Hewlett-Packard repair 
and service manuals involved. The 
manuals, and all major parts, can be 
had overnight via VISA/800. 

For some reason which 1 simply 
cannot fathom, Apple Computer ab- 
solutely insists tnat you use the HP 



w 
o 
z 
o 
ffi 
t- 
o 



LU 

6 

Q 
< 



NEW FROM 

DON LANCASTER 



HARDWARE HACKER STUFF 

Hardware Hacker Reprints II or III 24.50 

Incredible Secret Money Machine 12.50 

CMOS Cookbook 24.50 

TTL Cookbook 19.50 

Active Filler Cookbook 19.50 

Micro Cookbook vol I or II 19.50 
Lancaster Classics Library 109.50 

Enhancing your Apple I or II 17.50 

Apple Writer Cookbook 19.50 

Apple Assembly Cookbook 21.50 

Absolute Reset He S, He 19.50 

Enhance 1 or II Companion Disk 19.50 

AppleWrlter CB or Assy CB Disk 24.50 

POSTSCRIPT STUFF 

Ask The Guru Reprints I, II or III 24.50 

LaserWriter Secrets (lle/Mac'PC) 29.50 

PostScript Show & Tell 39.50 

Intro to PostScript VHS Video 39.50 

PostScript Beginner Stuff 39.50 

Pos 1 5c r Ipt Co ok b o o k ( Ado be ) 16.50 

PostScript ftef. Manual (Adobe) 22.50 
PostScript Program Design (Adobe) 22.50 

Type I Font Format (Adobe) 15.50 

LaserWriter Reference (Apple) 19.50 

Real World Postscript (Roth) 22.50 
PostScript Visual Approach (Smith) 22.50 

Thinking In PostScript {RelrJ) 22,50 

The Whole Works (all PostScript) 299.50 



FREE VOICE HELPLINE 



VISA/MC 



SYNERGETICS 

Box 809-RE 

Thatcher, AZ 85552 

(602) 428-4073 



CIRCLE 83 ON FREE INFORMATION CARD 



service manuals to keep your Apple 
LaserWriter printers alive. As near as 
I can tell, this is some sort of a top- 
secret rebate policy. 

At any rate, you can recognize the 
older CX cartridges by their large 
three-inch drums, their red-yellow- 
green end dial, and their obvious 
lunchbox handle. While the original 
LaserWriter and all similar printers 
using them are rather dated, they do 
remain useful, especially when print- 
ing lots of heavier stock. Many used 
bargains are now cropping up involv- 
ing these machines. Two sources are 



Don Thompson and The Printer 
Works. 

Non-PostScript laser printers, of 
course, are an utterly useless ripoff, 
so be absolutely certain that your 
used machine can speak genuine 
Adobe PostScript. 

Before we begin, note that the pho- 
tosensitive drums must newer be ex- 
posed to strong light, or to any light at 
all over any long period of time. Never 
get fingerprints on the drum. Cotton 
gloves are a good idea. 

Toner is an ultra fine powder that 
can end up all over everything. It is 
sometimes best to work outside, 
possibly wearing a mask. Toner can, 
in theory, explode a vacuum cleaner, 
but that rarely will happen. But do be 
careful. 

The general steps in refilling any 
cartridge are fivefold: 

(1) Remove and discard any waste 
toner from the spent toner holding 
tank. Do not reuse the spent toner. 

(2) Refill your fresh -toner supply tank 
with a new bottle. 

(3) Lubricate the drum with a light 
dusting of Pixie Dust (see below). 

(4) Replace the oiled wiper felt on the 
fusion assembly elsewhere in the 
printer. 

(5) Update accurate life and service 
records on a suitable label. 

Figure 2 shows you those CX refill- 
ing details. There is really never any 



To refill an older CX cartridge with the punch-and-go method, you first 
snap off the cardboard label and then drill a toner filling hole... 



~©~ 



Dfili a F.--.S inch. ho>* using 
1 13 ViEt Grip LTn tjit: 
t aro'uliy diar all ctiipi. 




A second CX hole is needed to let you empty the spent toner holding tank. 
This area is found underneath the cartridge... 




Drill VI inch fwlfl uunj 
. * M Vni G'ip UniWt; 





r "•""""" 






4 




© 













FIG. 2— THE CX CARTRIDGE is easily recognized by its large drum and its obvious 
"lunchbox" handle. Here are my "punch-and-go" refilling secrets. 



66 



The SX cartridge punch-and-go refilling process is similar to the CX, 
except for the hole locations. The filter hole is shown here... 



Drill 5)8 inch hole using 
a*3 Vise Grip Itmbil. 
caielully clear all chips 



I 



] 



One or more spent toner drain holes must also get added to the SX 
cartridge. The plastic is thin, so use a conical step drill... 




Drill 3/B Inch hole using 
a 13 Visa Grip Umblt; 
carefully clear all chips 



Be curiam thai Ihe new 
Mole is cantered between 
Ihe die sink marks! 




^^^____/ « 



FIG. 3 — THE SX CARTRIDGE is wider than it is high, has a small drum, and is the most 
popular cartridge for the larger 8- PPM PostScript laser printers. 



reason to tear down a CX cartridge, 
except to substitute a hard drum. The 
original factory drums are big enough 
that you can often get four or five 
refills as is. For most people most of 
the time, a total teardown will cause 
many more problems than it will sol- 
ve. Remember that your ultimate goal 
should be minimizing all of your per- 
page toner costs, not maximizing the 
number of recharges for each drum. 
An extra recharge is pointless if it 
costs the end user more per page to 
do so. 

if you absolutely have your heart 
set on taking a CX cartridge apart, 
you'll need two special tools. One is a 
special tamperproof Torx bit. This is 
EVCO part number #945B700 and is 
available from Jensen Toots as well as 
most refilling supply houses. The 
second is a special pin-pulling tool 
called a CX C lorn pens tractor and 
available once again through Don 
Thompson. 

Should you use my punch and go 
method, you will have to drill two 
holes in the cartridge on your first 
reload. That is best done using a 
rather unusual step-drill called a #3 
Vise Grip Unibit. They are available 
from Jensen Tools or from any larger 
electrical contracting supply house. 
When used with a variable-speed 
hand drill, the Unibit cleanly cuts a 
perfectly round hole in brittle plastic, 



while producing a single and easily 
grabbed chip. 

After drilling the holes, the spent 
toner is shaken or vacuumed out. You 
can reseal the hole with plain old 
Scotch Tape (be VERY careful to get 
a secure seal!), or else use a nickel 
Caplug. Your fresh-toner hole is sim- 



ilarly used to accept a bottle of new 
toner and then resealed. 

Figure 3 shows you the SX car- 
tridge recharging. The LaserWriter 
NTX is a typical machine that uses 
this cartridge. The SX cartridges have 
a one-inch drum and are rather flat 
looking, being much wider than thick. 
Should you decide to tear down the 
cartridge or upgrade to a hard drum, a 
different glompenstractor is needed 
having a narrower snout. 

The details of my punch-and-go re- 
fill method remain pretty much the 
same. First time around, you drill a 
suitable filling and emptying hole. 
Once again, the #3 Vise-Grip Unibit 
in a variable-speed hand drill is ideal 
for this. To refill, drain and discard the 
spent toner and reseal. Then fill the 
fresh toner tank and reseal. 

Figure 4 shews you the newest LX 
cartridge recharging. The personal 
laser printers, such as the QMS 
PS-410, use this cartridge. The LX 
cartridge is recognized by its small 
size, an obvious spring, and its 
"white trim" gears and bearings. 

No holes are required. To access 
the tank, pull the two pins by using 
ChannelLock #357 end pliers. The 
tank can then be refilled through the 
existing Caplug. To change the drum 
or drain the spent toner, remove the 
four Phillips screws on those nylon 
drum bearings and pull the drum. 






The LX cartridge does not need any modifications before any refill, hard drum 
upgrade, or any spent toner draining... 



FIRST, remove this spring 
using a homemade "J" tool. 




THIRD. Remove the screws 

to change the hard drum or 

drain out the spent toner, 



SECOND, pull these pins to 
remove the fresh toner tank 
for easy refilling. 



But be EXTREMELY careful not to touch the photosensitive drum or expose It 
to any strong light or ANY light of long duration. 

FIG. 4— THE SMALLER LX CARTRIDGE is used in the "personal" 4-PPM printers and is 
easily spotted by its obvious spring and the "white trim." NEVER use copier toner in a 
laser printer. 



2 

-4 

to 



67 



Spent toner can be simply vacuumed 
or shaken out. 

After a recharge, it's a good idea to 
very lightly dust any drum with a suit- 
able lubricant. Many of them are 
based on plain old zinc sterate. Only 
don't substitute baby powder since 
the perfume and oils will do you in. 
The usual name here is Pixie Dust. 
Pixie dust is available through most 
recharging supply houses at very low 
cost. You can make a "duster" from 
the toe of a child's athletic sock and a 
rubber band. 

Once again, the wiper pad on the 
fusion assembly should get replaced 
every time you change the cartridge. 
You normally keep the old wiper wand 
and drop a new peel-and-stick oiled 
nomex felt strip in place. 

While you can obtain toner-tank re- 
sealing strips, travel of any kind is 
extremely rough on toner cartridges. I 
do not recommend ever moving a car- 
tridge further than you can gently and 
personally hand carry it. Nor do I rec- 
ommend ever swapping your own car- 
tridges for unknown outsiders. I 
strictly limit my personal recycling 
service to a six-mile radius. Yours 
also should be. 

Reuse of toner removed from 
spent-toner holding tanks is not in the 
least recommended, nor is recycling 
your own wiper pads. 

There does remain plenty of "zoo" 
aspects to toner recycling. Certain 
irresponsible manufacturers have be- 
gun some high-profile national "recy- 
cling" programs which in fact destroy 
the cartridges rather than recycling 
them. The hope here is to perma- 
nently get the cartridges out of cir- 
culation before they could be refilled 
and reused. Only an absolute idiot 
would participate in any program of 
this sort. 

If you do nothing else, you can sell 
your empty cartridges locally for $5 
to $10 each, and then contribute as 
much of the proceeds as you care to 
to your favorite environmental group. 

Any salesman that tells you that 
normal use of a properly recycled car- 
tridge automatically voids your printer 
warranty is telling you an outright lie 
for which they can be criminally pros- 
ecuted. Some others are literally gold 
plating stuff that does not in the least 
need to be gold plated. Yet others 
substitute shoe polish for proper 
hard-drum recoating. 

Those recharge/repair schools run 
the gamut from outstanding high- 




FIG. 5— A "SANTA CLAUS" MACHINE for producing large display letters. The poly- 
ethylene bead from the glue gun is programmed to bui Id up the entire letter one strand at a 
time. While slow, there are no mold charges and the size and style can be instantly 
changed. Logos and custom characters are a snap. 



quality bargains down to outright 
ripoffs. To tell one from another, ask 
the school for a list of all previous 
students in your area. Then call one 
or two of them. 

So, you will have to pay careful 
attention to details. But the toner re- 
charging industry is fast maturing and 
now offers all sorts of exciting and 
cost-saving new hardware- hacking 
opportunities. 

A great telephone book 

I'm often asked how I can usually 
find helpline names and numbers so 
fast. Well, I have built up my own re- 
source data base over the years, and 
that is where I will often look first. 
Physically, this is just a big black note- 
book with lots of stuff that keeps fall- 
ing out of it. Most of this data base 
appears in the Hardware Hacker re- 
prints, and a downloadable and anno- 
tated selection of the best of the best 
appears on my GEnie PSRT library as 
file #80 MYFAVOR.TXT. 

But the number- two place I always 
go to is the Electronic Industry Tele- 
phone Book from Harris Publishing. 
While it lists for around $50 per year, 
sometimes you can get a free one or 
promo copy from a sales rep. 



This national coverage gem works 
just like any other phone book, with 
alphabetical white pages and by-topic 
yellow classifieds. Their listings are 
very thorough, and 1 am continually 
amazed by how often this one volume 
can solve so many problems. 

Santa Claus again 

Several times now, we've taken a 
look at the new Santa Claus ma- 
chines that create instant desktop 
prototypes at a tiny fraction of the 
time and cost of traditional methods. 
As we have seen, all the stuff out 
there so far is primitive, klutzy, and 
horrendously priced. At least so far. 

We've also seen some outstand- 
ing new hacker opportunities here, 
that range from low-cost desktop 
prototyping alternatives to offering 
yourown prototyping service bureaus 
using the commercial systems. 

While the best possible desktop 
prototyping solution remains "none 
of the above," let's look at a pair of 
new alternatives. 

Have you ever played around with 
your glue gun? While not readily avail- 
able, you can get polyethylene rods 
to use as glue sticks. That gives you a 
method for encapsulating compo- 



68 





NAMES AND NUMBERS 






Anderson Power Products 


GEnie 


Printer Works 




145 Newton Street 


401 North Washington Street 


3431 Arden Road 




Boston, MA 02135 


Rockvtlle, MD 20850 


Hayward, CA 94545 




(617) 787-5880 


(800) 638-9636 


(800) 235-6116 




CIRCLE 301 ON FREE INFORMATION CARD 


CIRCLE 308 ON FREE INFORMATION CARD 


CIRCLE 315 ON FREE INFORMATION CARD 




Black Lightning 


Harris Publishing ElTD 


Recharger 

3870 Lb Sierra Avenue S266 




RR 1-87 Depot Road 


2057-2 Aurora Road 


Riverside, CA 92505 




Hartland, VT 05048 


Twinsburg, OH 44087 


(714) 359-8570 




(800) BLACK99 


(216) 425-9000 


CIRCLE 316 ON FREE INFORMATION CARD 




CIRCLE 302 ON FREE INFORMATION CARD 


CIRCLE 309 ON FREE INFORMATION CARD 


Rohm 

8 Whatney 




Caplug 


Hewlett-Packard/Manuals 


Irvine, CA 92718 




2150 Elmwood Avenue 


19310 Pruneridge Avenue 


(714) 855-2131 




Buffalo, NY 14207 


Cupertino, CA 94014 


CIRCLE 317 ON FREE INFORMATION CARD 




(716) 876-9855 


(800) 752-0900 






CIRCLE 303 ON FREE INFORMATION CARD 


CIRCLE 310 ON FREE INFORMATION CARD 


Rotary Flight International 

5555 Zuni SE, Ste 281 
Albuquerque, NM 87108 




CopyMate Products 


Lazer Products 


(505) 298-9362 




20F Robert Pitt Drive 


12741 E Caley Avenue #130 


CIRCLE 318 ON FREE INFORMATION CARD 




Monsey, NY 10952 


Englewood, CO 80155 






(800) 457-0074 


(303) 792-5277 


Sony Semiconductor 




CIRCLE 304 ON FREE INFORMATION CARD 

Cory Laboratories 


CIRCLE 311 ON FREE INFORMATION CARD 


10833 Valley View Street 






Cypress, CA 90630 




LSI Logic 


(714) 229-4195 

CIRCLE 319 ON FREE INFORMATION CARD 




Box 261, 823 5th Street 


1551 McCarthy Blvd 






Menominee, Ml 49858 


Milpitas, CA 95035 


Statek 




(906) 863-9336 


(408) 433-8000 


512 N Main Street 




CIRCLE 305 ON FREE INFORMATION CARD 


CIRCLE 312 ON FREE INFORMATION CARD 


Orange. CA 92668 
(714) 639-7810 
CIRCLE 320 ON FREE INFORMATION CARD 




Crystek 


Maxim 






2351/2371 Crystal Drive 


120 San Gabriel Drive 


Stratasys 




Ft Myers, FL 33907 


Sunnyvale, CA 94086 


7411 Washington Avenue S 




(813) 936-2109 


(408) 737-7600 


Minneapolis, MN 55439 




CIRCLE 306 ON FREE INFORMATION CARD 


CIRCLE 313 ON FREE INFORMATION CARO 


(612) 941-5607 






CIRCLE 321 ON FREE INFORMATION CARD 




EVCO 


National Sandblast 


Don Thompson 




PO Box 36339 


4421 Prospect NE 


23072 Lake Center Drive #100 




Birmingham, AL 35236 


Albuquerque, NM 87110 


El Toro, CA 92630 




(205) 822-5381 


(505) 883-1151 


(714) 855-3838 




CIRCLE 307 ON FREE INFORMATION CARD 


CIRCLE 314 ON FREE INFORMATION CARD 


CIRCLE 322 ON FREE INFORMATION CARD 





nents in high-quality plastic or making 
your own custom connectors. Or of 
doing plastic casting at a tiny fraction 
of the usual mold costs. 

Let's carry this one step further as 
shown in the crude system of Fig. 5. 
Say you wanted to produce some 
large display letters in various styles 
and sizes. Just take a modified glue 
gun on a linear stepper and a no-stick 
base on a second linear stepper, and 
you should be able to put a plastic 
bead down that follows the shape of 
the letter. Repeat the process until 
the entire letter is created. The host 
computer traces out the proper path 
to build up the letter one bead at a 
time. 



Admittedly, this is a rather crude 
system which is limited to thin two 
dimensional objects. And we haven't 
properly addressed the third dimen- 
sion at all. But it is a good starting 
point that could lead to some exciting 
new developments. 

One suitable stepper would be the 
Hurst model SLS. I've been meaning 
to work up some more details on this 
and on Hurst's new EPC-015 control- 
ler. Maybe in a future column. 

There is a commercial variation of 
the "hot glue gun" desktop prototyp- 
ing method. This is the brand new 
Stratasys 3-D Modeler. They refer to 
their process as Fused Deposition 
Modeling, or FDM. 



The system starts with a large roll 
of .020 or .050 diameter plastic or 
wax filament. The filament is heated 
just enough to make its outside tacky. 
The filament is then laid down into an 
existing pattern in the same way you 
can do artsy-craftsy stuff with string 
soaked in glue. 

A three dimensional object is then 
built up, literally one string at a time. 
While they have an elaborate CAD 
software system based upon 
NURBS splines, the PostScript lan- 
guage and any old word processor 
should be able to do a vastly better s 
job far faster and much cheaper. $ 

The FDM method seems es- J 
peciatly well-suited for modeling con- 5 



tainers and other hollow packaging 
products. But sharp edges appear 
tricky to do, especially gear teeth. 
Ultimate costs should be low, since 
no lasers, fumes, high temperatures, 
costly materials, or exotic chemicals 
are involved. The typical speeds ap- 
proach 1000 inches per minute. 

One big problem with the system: 
Some prototypes can end up looking 
like something that missed hitting the 
reject bin in the arts and crafts class. 
Finer filaments can cure this, but build 
more slowly. 

I'm wondering if a better prototyp- 
ing solution might not involve two 
steps. Homes are usually built in a 
"rough" and "finish" stage. And ma- 
chinists often work with near net 
stock to try and minimize their total 
production time. And modelers will 
often build their model first and then 
superdetail it later. 

So perhaps the solution is some 
system that gets the shape pretty 
near the way you want it quickly and 
crudely. A second step would then 
measure and modify what you have to 
give for your final precision fit and 
finish. Let's have your thoughts on 
this. 



VHF AND MICROWAVE RE- SOURCES 



ARRL Handbook 

225 Main Street 
Newington, CT 06111 

CIRCLE 323 ON FREE INFORMATION CARD 



Defense Electronics 

6300 South Syracuse Way, Ste 650 
Engiewood, CO 80111 
(303) 220-0600 

CIRCLE 324 ON FREE INFORMATION CARD 



Fair Radio Sales 

PO Box 1105 
Lima, OH 45802 
(419) 227-6573 

CIRCLE 325 ON FREE INFORMATION CARD 



Hewlett-Packard 

PO Box 10301 

Palo Atto.CA 94303 

(415) 857-1501 

CIRCLE 326 ON FREE INFORMATION CARD 



M/ACom Semiconductor 

43 South Avenue 
Burlington, MA 01803 
(617) 272-3000 

CIRCLE 327 ON FREE INFORMATION CARD 



Mini-Circuits Labs 

PO Box 350166 
Brooklyn, NY 11235 
(718) 934-4500 

CIRCLE 331 ON FREE INFORMATION CARD 



Motorola 

5005 E McDowell Road 
Phoenix, AZ 85008 
(800) 521-6274 

CIRCLE 332 ON FREE INFORMATION CARD 



Nuts & Volts 

Box 1111 

Placentia, CA 92670 
(714) 632-7721 
CIRCLE 333 ON FREE INFORMATION CARD 



Plessey Semiconductor 

13900 Alton Pkwy, Ste 123 
Irvine, CA 92718 
(714) 455-2950 

CIRCLE 334 ON FREE INFORMATION CARD 



Radio Research Instruments 

584 North Main Street 
Waterbury, CT 06704 
(203) 792-6666 

CIRCLE 335 ON FREE INFORMATION CARD 



to 

'O 

z 
Q 

L" 
h- 

o 

LU 



VHF and microwave 
resources 

There are all sorts of interesting 
things going on in those VHF and 
microwave frequencies found above 
several hundred megahertz. Amateur 
television, weather fax reception, ca- 
ble services, satellite downlinks, cel- 
lular phones, sports radar, remote 
controls, radio astronomy, emergen- 
cy services, garage doors, al- 
timeters, instrumentation, microwave 
ovens, and video links are a few ex- 
amples of hackable opportunities in 
the VHF and microwave frequency 
areas. 

Unfortunately, all of the hacking 
rules change in the VHF and micro- 
wave range. First, you no longer have 
individual resistors, capacitors, and 
inductors. 

Instead, the individual resistance, 
capacitance, and inductance of each 
component has to be uniquely taken 
into account, and often done so in a 
distributed manner. Circuit strays can 
quickly become totally intolerable. 
Tolerances of a few thousandths of 
an inch can make or break a circuit's 
performance. 

Second, testing and measurement 
often has to be indirect, because 



Microwave Journal 

685 Canton Street 
Norwood, MA 02062 
(617) 769-9750 

CIRCLE 328 ON FREE INFORMATION CARD 



Microwave Product Digest 

34 Evergreen Piace 
Tenalty, NJ 07670 
(201) 568-5835 

CIRCLE 329 ON FREE INFORMATION CARD 



Microwaves & RF 

611 Route #46 West 
Hasbrouck Heights, NJ 07604 
(201) 393-6286 

CIRCLE 330 ON FREE INFORMATION CARD 



many attempts to directly measure a 
microwave circuit could severely dis- 
rupt what you are trying to measure. 
Not to mention the high frequencies 
and weak signal levels involved. Most 
suitable test equipment also tends to 
be very specialized, arcane, and quite 
expensive, and hard to justify. 

Third, VHF and microwave parts 
can be ridiculously costly, since most 
of them are aimed at gold-plated low- 
volume military uses. 

Fourth, the math, the field theory, 



Rogers 

100 S Roosevelt Avenue 
Chandler, AZ 85226 
(602) 961-1382 

CIRCLE 336 ON FREE INFORMATION CARD 



SGS-Thomson Microelectronics 

211 Commerce Drive 
Montgomeryville, PA 18936 
(215) 362-8500 

CIRCLE 337 ON FREE INFORMATION CARD 



Surplus Trader 

Winters Lane Box 276 
Alburg, VT 05440 
(514) 739-9328 

CIRCLE 338 ON FREE INFORMATION CARD 



and the advanced technical skills 
needed to do anything useful at these 
frequencies goes way beyond elec- 
tronic fundamentals. A lot of useful 
microwave information tends to re- 
quire advanced skills, can be hard to 
find, and is often classified. 

And finally, much of microwave de- 
sign work is far more art than sci- 
ence. To this day. black magic can be 
involved, and you either have the right 
feel for what you are doing, or your 
circuits simply will not work. 



70 



For this month's resource sidebar, I 
have tried to gather together some 
VHF and microwave stuff you might 
find of interest. Obviously, you'll want 
to start with that Radio Amateur's 
Handbook published by the ARRL. 
Many of the ham magazines and club 
activities will also involve the VHF 
and microwave frequencies. Per a re- 
cent rule change, certain new ham 
licenses don't require Morse code. 

By far the leading surplus house 
carrying microwave radar goodies is 
Radio Research Instruments. How- 
ever, these folks tend to concentrate 
on whole systems and refuse to 
show prices in their flyers. Alternate 
places to look include Fair Radio 
Sates, Surplus Traders, and in the 
Nuts and Volts shopper. 

While utterly ancient, McGraw 
Hill's MIT Rad-Lab series should still 
be scrounging around on the dusty 
back shelves of the larger technical 
libraries. Volume One in particular, 
Ridenour's Radar System Engineer- 
ing has been reprinted a number of 
times and remains highly useful to 
this day. Another more recent classic 
is Merrill Skolnik's Introduction to 
Radar Systems 

As with any field, the free trade 
journals are your foremost day-to-day 
resource. While there are several 
dozen, four I've found useful include 
Microwaves and RF, the Microwave 
Journal. Microwave Product Digest, 
and Defense Electronics. 

Be sure to check out Mini-Circuits 
Labs for their low-cost broadband 
amplifier chips, and Plessey for their 
unusual Satellite Cable and TV Inte- 
grated Circuit Handbook. They also 
have lots of info on frequency syn- 
thesis and high-speed dividers. 

Hewlett Packard, of course, makes 
all kinds of microwave components, 
as well as high-performance micro- 
wave and VHF test instruments. And 
Motorola has a wide variety of high- 
frequency semiconductors and ap- 
plication notes available. 

Two other chip sources include 
SGS and M/A Com, while Rogers 
supplies printed-circuit materials and 
dielectrics useful for microwaves. 

Well, that should be enough to get 
you started. Please let me know what 
else you think should be added to our 
resource files. 

New tech literature 

From Sony, there's a new Memory 
Data Book. They also have lots of 



great stuff on A/D and D/A convert- 
ers. From Rohm, there's an Electronic 
Components Catalog which includes 
details on their FM stereo broad- 
casters and lots of other goodies. 

From LSI Logic, there's a new 
group of LR64700 video-compres- 
sion chips that should revolutionize 
both still- and moving-picture image 
storage and transmission. 

I get lots of calls asking about 
hacker-friendiy sources for custom 
crystals. Two of my favorite sources 
are Statek for low frequencies and 
Crystek for higher frequencies. Both 
have catalogs, data sheets, and ap 
notes available. 

A new detailed bibliography on 
magnetic refrigeration is available 
through Jerry Hagen at his Cory Lab- 
oratories. Our unusual hacker maga- 
zine for the month is Homebuilt 
Rotorcraft from the Rotary Flight In- 
ternational folks, while that free 
Maxim Engineering Journal has all 
sorts of semiconductor goodies in it. 
Especially for audio/ video switches 
and power supplies that work off a 
single AA cell. 

Free samples of Powerpole con- 
nectors are available from Anderson 
Power Products Inc. These are both 
snap-together modular and sexless. 
They should be ideal for such things 
as solar panels. 

An interesting sandblasting cata- 
log is available from National Sand- 
blast. This is one quick way to spruce 
up any metal on your prototypes. 

Turning to my own products, for the 
fundamentals of digital integrated cir- 
cuits, do check into my TTL Cook- 
book and CMOS Cookbook. Or to 
pick up all the goodies at once, try my 
Lancaster Classics Library. 

We also now have the Hardware 
Hacker III reprints available, which 
has the latest and best of all these 
columns in them. All edited, revised, 
corrected, and indexed. 

Finally, I do have a new and free 
mailer for you which includes dozens 
of insider hardware hacking secret re- 
sources. Write or call for info. Our 
usual reminder here that most of the 
items mentioned appear either in the 
Names and Numbers or in the 
Microwave Resources sidebars. 

As always, this is your column and 
you can get technical help and off- 
the-wall networking per that Need 
Help? box. The best calling times are 
weekdays 8—5, Mountain Standard 
Time. Let's hear from you. R-E 



DIGITAL VIDEO STABILIZER 
ELIMINATES ALL VIDEO COPY 
PROTECTIONS 




While watching renlal 
mtwi*s t you will notice an- 
noying periodic color 
darkening, color shift, un- 
wanted lines, Hashing or 
Jagged edges. This is 
caused by the copy protec- 
tion jamming signals em- 
bedded in the video tape, 
such as Macrovision copy 
protection. Digital Video 
Stabilizer RXII completely 
eliminates ail copy protec- 
tions and Jamming signals 
and brings you crystal dee/ 
pictures. 

FEATURES: 

• Easy to use and a snap 
to Install 

• StBte*oMh*-aj1 in- 

tngratsd circuit t ecfinol- 

• 1 56% automatic - no 
need for any 

troublesome adjust- 
ments 
•Compatible to all types 
ofVCRiandTVa 

• The best and most excit- 
ing Video Stabilizer in 
the mark*. 

• light welghl (8 ounces) 
and Compact (1x3.5x5 ) 

• Beaulif ul deluxe gift box 

• Uses a standard 9 Volt 
battery which will lasl t- 
2 years. 



WARNING : 

SCO 

Electronics and 
RXII dealers do 
not encourage 
people to use 
the Digital 
Video Stabilizer 
to duplicate 
rental movies 
or copyrighted 
video tapes. 
RXII is in- 
tended to stabi- 
lize and restore 
crystal clear 
picture quality 
for private 
home use only. 

( Dealers Welcome 1 



ToOrder: $49.95 ea + $4 lot FAST UPS SHIPPING 

1-800-445-9285 or 516-568-9850 

Visa, M!C, COD MR 9-6 (baltery not Included) 

SCO ELECTRONICS INC. 

DeplCRE5561 W. Merrick Ftd. Valley Stream NY t 1580 

Unconditional 30 days Money Back Guarantee 



CIRCLE 178 ON FREE INFORMATION CARD 



CABLE TV 
DESCRAMBLER 

How You Can Save Money 
ibie Rental Fees 



Kpg 



1 Unit 5+ 

Jerrold SB w/Tri-BL. $» tTO ..„.„ . . 

SupcrTri-Bi (IBM). ...... J 109....I75 US Cable will 

Jerrold 450 combo, S189 ...$139 Beat Anyone's 

Scientific Atlanta S109.,.,J7J Prl,» 

SA S53& 1250....$ 19S ... r _V, c<! :., 

Pioneer- S109....S79 Advertised In 

Oat KN 12 (w/VS) SIM .. . WS this M aeaiine ! 

I lamlin MLD 1200. SS9. 159 3? 

Tocorn..._ S1W....H29 

Stargate converter SS9. 169 

Panasonic TZPC145 $99. S79 

30 Days Money Back Guarantee 
Free 16 page Catalog 

Visa, M/C, COD or send money order to: 

US Cable TV Inc. dcpikres 

4100 N.Powerline Rd., Bldg F-4 
Pom pa no Beach, FL 33073 

1-800-445-9285 

For Our Record 

I, [he undersigned, do hereby declare under penalty of per- 
jury that all products purchased, now and in the future, will 
only be used on Cable TV systems wi tbproper autboriza t ion 
from local official* or cable company officials in accordance 
with all applicable federal and state ton FEDERAL AND 
VARIOUS STATE LAWS PROVIDE FOR SUBSTANTIAL 
CRIMINAL AND CIVIL PENALTIES FOR UNAUTHORIZED 
USE. 
Dale: 

Signed : 

No Florida Sales! 

CIRCLE 179 ON FREE INFORMATION CARD 



71 



AUDIO UPDATE 



Japan: The Evolution of an Audio Colossus 



LARRY KLEIN 



It may seem strange to audio new- 
comers, but in the early days of hi- 
fi — the 1950s — there were no 
Japanese components in the U.S. 
There was, however, a Japanese do- 
mestic audio market. I remember 
reading about the hi-fi coffee houses 
with sophisticated sound systems 
that dotted Tokyo. As further evi- 
dence, Audio magazine ran intermit- 
tent ads from a Tokyo company called 
Fukuin Electric. Their Pioneer brand 
products included various drivers 
plus "An Ideal All-Purpose Amplifier 
for Home High Fidelity Systems" that 
was actually an AM/FM shortwave 
receiver. Neither a price nor a U.S. 
source was mentioned in any of the 
ads, so one can assume that Fukuin 
was trying to attract distributors 
rather than mail-order customers. 
True, there was a line of Japanese 
open-reel tape recorders being sold 
by a California distributor called Su- 
perscope; few knew or cared that 
they were being made by Sony, an- 
other unknown Japanese company. 
And so things went for several years. 

The Japanese invasion 

The Japanese entry into the audio 

market started relatively slowly. In 

1966, as Technical Editor of Stereo 

Review, I arranged for the first lab 

test of a Japanese receiver. Made by 

Kenwood, it appeared to have nothing 

terribly innovative about its circuitry, 

but it was a fine performer and very 

well made by U.S. standards. We 

judged it to be an excellent value. 

Within six months of our report, an 

upgraded model appeared with four 

times the power and greatly improved 

FM performance. The kicker was that 

^ it sold for exactly the same price 

z ($239.95) as the earlier unit! If I had 

2 been an American audio manufac- 

5 turer at the time, I would have be- 

il come very nervous! 

^ There was another aspect of the 

5 Kenwood review worth mentioning. 

r Bear in mind that this all took place 



long before the FTC became involved 
in amplifier specifications, and most 
audio manufacturers were, let us say, 
somewhat "optimistic" when report- 
ing their specs. When Mr. Kasuga of 
Kenwood called to ask how the report 
was coming, I told him that it was fine 
and the unit easily met all its specs 
except for a slight rise in distortion 
below 50 Hz. 

To my surprise, Kasuga became 
upset and stated that his receiver 
was free of such problems. I asked 
our lab to retest the unit; the results 
were the same. After a great deal of 
back-and-forthing it turned out that 
one of our lab meters had developed 
a fault that caused the spurious large 
distortion reading. I hadn't originally 
given the out-of-spec distortion a 
second thought because virtually all 
previously tested U.S. -made re- 
ceivers showed far higher distortion 
at the same frequencies. 

Quality control 

A quality-control engineer once 
said to me that quality is not some- 
thing you inspect into a product after 
it's built — it should be designed in 



right from the outset. I later learned 
that this was one of the prime pre- 
cepts of W. Edwards Deming. who is 
generally regarded as the father of 
quality-control methodology, Com- 
paratively unknown in the U.S., in the 
early 1950s Deming started teaching 
Japanese managers and engineers 
how to manufacture quality compo- 
nents. Deming was subsequently 
awarded a medal and a citation by 
Emperor Hirohito that credited him for 
the rebirth and worldwide success of 
Japan's industry. 

The quality concept was one that 
the Japanese obviously took to heart 
early on in all aspects of their audio 
(and camera) manufacturing careers. 
For example, during my first visit to 
Japan in the early 1970s, I bought, 
among other items, a prerecorded 
cassette from a street display outside 
a Ginza department store. The cas- 
sette was chosen simply because I 
was amused by its jacket showing 
what appeared to be a Japanese 
country-and-western rock group. 
When I went to play the cassette at 
home I immediately noticed two 
things: (1) It was not Dolby encoded. 




A QUALITY-CONTROL STATION in Yamaha's Hamatsu Plant, 



'2 



and (2) it was quieter than most of my 
prerecorded cassettes that included 
Dolby noise reduction. 

My subsequent experiences with 
Japanese LP's and prerecorded 
open- reel tapes were similar. The 
Japanese tapes were quieter, the rec- 
ords were flatter and had better sur- 
faces, and both had lower distortion 
and a wider frequency range than the 
usual U.S. products. And when I first 
visited Japan. I was so impressed by 
the clarity, detail, and color of their TV 
transmissions that I assumed that 
they were using some system other 
than the U.S. -standard NTSC. How- 
ever when some U.S. -made pro- 
grams were broadcast, it became 
apparent that the superiority of the 
Japanese picture was due solely to 
the care exercised in its production. 
So. too. with the records and tapes. It 
was evident that Japanese engineers 
and production people gave a damn 
about their products, an attitude that 
apparently was and is somewhat rare 
in the U.S. In short. Doming 's quality- 
control methodology provided the 
tools, the Japanese workers and 
management provided the attitude — 
and the rest is history. 

Japanese marketing 

When Japanese audio products 
began to appear in the U.S., they 
were mostly brought in by U.S. dis- 
tributors, such as Superscope men- 
tioned before. Some American 
marketeers did a creditable job; 
others didn't seem to realize exactly 
what they had. For example, I re- 
member a company called Nivico 
whose product line included several 
models of German fake fireplaces 
complete with a bar, glasses, and a 
"hi-fi" system. This less-than-high- 
tech company also distributed JVC's 
top-of-the-line audio equipment. I re- 
member seeing a JVC preamplifier 
with pink-noise source and multi- 
band equalizer on sale in Macy's ra- 
dio department. I have no idea how 
many were sold — and whether the 
buyers were told that they would also 
need a power amplifier, speakers, 
and a tuner in order to hear music. 

In any case, most Japanese man- 
ufacturers ultimately bought them- 
selves back from their distributors, 
some came over on their own, and a 
few bought U.S. hi-fi companies such 
as Fisher — via Emerson Radio — and 
proceeded to design and manufac- 
turer the products in Japan. Some 



Cable TV 

Descrambler Article Parts 

We stack the exact Parts, PC Board and Adaptor for several articles published 
in Radio-Electronics magazine on building your own Cable TV Descrambler. 



February 1984 
SB-3 Type 

701 Parts Pkg $19.00 

Includes alt original parts. 

702 PC Board 7.95 

Original 3X4 etched, drilled 
and Silk- Screen pc board. 

704 AC Adaptor 7.95 

IS to 18 Volt DC@ JDOma. 

701, 702 & 704 29.00 

All three lor special saving. 



February 1987 
Tri-Mode 

301 Parts Pkg 29.00 

Includes all original parts. 

302 PC Board 7.95 

Original 5X8 etched, drilled 
and Silk-Screen pc board. 

304 AC Adaptor 7.95 

T2 to 18 Volt DC ® 200m*. 

301, 302 & 304 39.00 

All three tor special savings. 

Tri-Mode Tutorial. .7.95 
20 pages of In-depth into. 



May 1990 
Universal 

901 Parts Pkg $49.00 

Includes all pans. 

902 PC Board 9.95 

Improved 4X7 etched, drilled 
and Silk- Screened pc board, 

904 AC Adaptor 8.95 

12 Volts AC @ 350mm. 

901, 902 & 904 59.00 

All three for special savings. 



Snooper Stopper.. .$39, 00 

Prevent Descrambler detection with snooper 
stopper/data blocker and protect your privacy. 
Includes tree article on Cable Snooping. 



Macrovision Kit. ..$29. 00 

Micro vision now you sen It, now you 

don't with our macro-scrubber kit. 
Originally Published in Radlo-Electronlcs , 



70 Channel Cable TV Converter $89.95 

* 6 Function Infra-Red remote, 

* Fine Tuning. 

* Memory & Recall, 



* Compatible with all External Descrambler. 

* Channel 3 & 4 switchable output. 

* $TD, HRC oj IRC compatible. 



CALL TOLL FREE 1-800-332-3557 



Outside USA Call 1-503-699-6935 
Visa, MasterCard and COD. 
Add $4.00 S&H, $6,50 Outside USA. 
D & 6 Electronics, Inc. PO Box 3310, 



VISA 



MC 



N. Attleboro, Ma. 02761 



CIRCLE 1S2 ON FREE INFORMATION CARD 



No Better Probe Ever at this Price! 




Shown here * ja 

Mode) SP150 Switchable Ix-lOx .... 4" 



Risetime less than 1.5 nsec. 



Free probe guide shews economical 
replacements for Tektronix. H.P. 
Philips and all others 



• Universal 
Works with alt oscilloscopes 

■ Rugged 
Flexible cable lasts longer- 
Replaceable ground lead 



• Economical 

Substantial savings compared to 
OEM probes 

• 10 Day Return Policy 

Guaranteed performance and quality 



PROBES, INC. 



TPI 



9178 Brown Deer Road, San Diego, CA 92121 
Toll Free 1-800-368-5719 



CIRCLE 123 ON FREE INFORMATION CARD 



w 

o 

z 
o 

o 



brands. Sansui for one. in effect 
came to the U.S. via Vietnam, where 
they were best sellers in the military 
PX's. At some point in time, the Japa- 
nese began to emulate U.S. auto 
makers by bringing out new models 
every year. Their self-imposed rules 
demanded that each new model in- 
clude some spec improvement — 
however minor — and/or a new circuit 
with wondrous properties. For exam- 
ple, during a visit to the Osaka Tech- 
nics factory, the engineers showed 
me a chart on which they had listed 
their upcoming "breakthrough" im- 
provements for each of the next 5 
years! 

Audio today 

One aspect of the Far-Eastern au- 
dio scene that I've not mentioned is 
their extensive private-labeling enter- 
prises. A friend who owns a U.S. 
company and manufacturing plant 
based in Washington state produces 
a wide range of audio equipment, 
some of which is built in the Far East. I 
asked him what determines which is 
made here and which is made there. 
His answer was simple: When he ex- 
pected to sell large numbers of a 
product — such as his medium-priced 
receiver— "economies of scale" 
made it far cheaper to have it man- 
ufactured overseas. On the other 
hand, limited-production compo- 
nents such as his very high-powered 
amplifiers can profitably be made in 
his U.S. plant. 

That explains why the limited pro- 
duction, "esoteric" audio products 
are mostly built in the U.S. or Great 
Britain, while high-volume products 
are made in the Far East. Of course, 
there are still a few American man- 
ufacturers who put out qualify com- 
ponents at both affordable and 
somewhat high-end prices. So if you 
are the type of person who insists on 
buying American, you still can. How- 
ever, it cannot be denied that the bulk 
of the electronics industry now be- 
longs to the Far East. I guess all of 
this has worked out pretty well for the 
U.S. audio consumer, in that you can 
get more bang for your audio buck 
than ever before. But for the Ameri- 
can manufacturers, or ex-manufac- 
turers, of audio components (and 
television sets, cars, and dozens of 
other categories), the Japanese 
manufacturing juggernaut has been 
an economic disaster. R-E 



PC1N 



continued from page 64 



2-a— c show how a modulated 
spread-spectrum signal used in 
direct sequencing is generated. 
When a carrier signal (a) is mixed 
with a noise signal (b), a broad- 
ening of the RF carrier occurs, 
resulting in a modulated spread 
spectrum (c). Modulation is ac- 
complished using the exclusive 
or logic operation. The effect of 
modulation is to reverse blocks of 
the wideband noise bits. Because 
the noise signal is much higher 
in frequency than the informa- 
tion signal, the resulting bit se- 
quence still appears to be 
random. The modulated signal Is 
actually the sum of the noise and 
signal bandwidths. 

You're probably wondering 
how the original information can 
be decoded at the receiving end. 
The information signal can be re- 
covered by modulating (exclusive 
or) a second time with the same 
noise waveform. Instead of mod- 
ulating the information signal 
with random noise, a PN gener- 
ator is used, which possesses 
many properties of wideband 
noise, but is exactly reproducible 
at remote locations. In order to 
remove unintentional noise in 
the receiver, multiple matched fil- 
ters are normally used. A block 
diagram of a typical direct se- 
quence is shown in Fig. 3. 

Even though signal spreading 
appears to be an inefficient use of 
spectrum for a single user, the 
theory suggests that many such 
transmitters can operate at the 
same time, on the same wide 
band, and in the same area, since 
each transmitter's intended re- 
ceiver will see only its code and 
ignore all others. In essence, this 
is code-division multiple access 
(CDMA). 

A spread-spectrum signal 
looks like low-level noise to a tra- 
ditional narrowband receiver, 
and can be designed so that it 
doesn't interfere with the tradi- 
tional receiver. In turn, a spread- 
spectrum receiver can be de- 
signed to ignore the interference 
of even multiple transmitters op- 
erating within its broad band- 
width. That resistance to inter- 
ference can apply to intentional 
interferers, such as other users 



of the spectrum, as well as spu- 
rious RF emissions created by 
many common household and of- 
fice appliances. 

The technique can be viewed 
as similar to a concert hall with a 
hundred pianos, each playing a 
different tune, and each member 
of the audience listening for one 
particular tune. As long as the 
listener can isolate that melody, it 
doesn't matter how many pianos 
there are (until the listener is 
deafened). 

Transmit power would gener- 
ally be at 1 milliwatt, but by using 
a technique called adaptive 
power control (APC), each base 
could monitor and adjust power 
levels of handsets to the mini- 
mum necessary to achieve com- 
munication without inter- 
ference. A reduction in emitted 
power through APC will permit a 
far larger number of simulta- 
neous users, so that at one milli- 
watt, one hundred simultaneous 
calls can be handled in a micro- 
cell within a 600-foot radius. 

TDMA 

Another technique being con- 
sidered is time-division multiple 
access (TDMA). TDMA works by 
dividing each second into 100 
ten-millisecond slots (as an ex- 
ample), and dividing each time 
slot into a number of frames, typ- 
ically 24. Half of those frames are 
then allocated for transmission 
from base stations to mobile 
units; and the other half are de- 
voted to transmission in the re- 
turn direction. Therefore, 12 
handsets could broadcast at the 
same time and place using the 
same frequency. That technique 
is used by PCN's in the United 
Kingdom, and is a technique that 
has been adopted for the cellular 
telephone systems in the United 
States when they become digital 
over the next few years. The dis- 
advantage of the technique is 
that it requires extremely precise 
timing and sophisticated elec- 
tronics. 

The FCC is now considering 
what action to take. Last June it 
launched an inquiry into 
whether PCN's are needed, what 
they will accomplish, what spec- 
trum should be allotted, if any, 
and how the new phenomenon 
should be regulated. Comments 
poured in from 110 companies, 
continued on page 92 



74 



moMiWMri.r v''<.'i:i: ,n iiMuymoi 


Let's build a simple, inexpensive logic probe for the 

home workbench. 







Even though the main reason for 
spending time at the bench is 
to wind up with a working cir- 
cuit, there are other good reasons for 
spending hours and hours hunched 
over a breadboard. Nothing ever 
works out the way you want it to, and 
that's especially true at the test 
bench. Dealing with unexpected Cor 
perhaps expected) design glitches is 
what makes bench time a great way 
to stretch your brain. 

Working your way through a proj- 
ect is a good learning experience, but 
only if you have the right equipment. 
For instance, a logic analyzer can in- 
stantly give you a window into the 
nitty gritty of a complex design. But 
there aren't many of us that can justi- 
fy parting with the kind of cash that's 
necessary to get your hands on a 
logic analyzer — or any other kind of 
exotic test equipment for that matter. 
That's especially true when the proj- 
ect has nothing to do with generating 
income. 

While there's no argument that 
high-tech designs can really be de- 
bugged only with high-tech equip- 
ment, you can do a lot of work with 
much simplerand less expensive test 
gear if you're willing to do a bit more 
work with your brain. High-speed cir- 
cuitry can be slowed down, gated 
latches can be added to catch 
pulses, andothersimilartrickscanbe 
pulled to snoop around a circuit. 

An extremely useful, but relatively 
inexpensive addition to any test 
bench is a logic probe. Now there are 
all sorts of different logic probes, and 
just how useful it can be depends on 
how many bells and whistles it has. A 
simple two-LED probe is about the 
bottom line, and the sort of informa- 
tion It can give you is just basic, bot- 
tom-line information. 

When designing a logic probe, you 
have to provide a way for the probe to 
operate with different logic families. 
That can complicate things slightly 
because each family — TTL, CMOS, 
etc.— has its own idea of what volt- 



ages constitute a high or low. Not 
only that, but some of them, such as 
TTL, also have about a one-volt dead 
band in which the whole idea of logic 
levels gets a bit murky. 

When you get right down to it, a 
logic probe is simply a circuit with the 
ability to detect and react to particular 
voltage levels. Anytime you're de- 
signing something like this and you 
plan on building it out of parts that are 
cheap and easily available (as we 
are), your mind should immediately 
turn to voltage comparators. 

A voltage comparator is really 
nothing more than an op-amp with a 
built-in hysteresis that makes it react 
sharply to voltages that cross a par- 
ticular threshold. You can build one 
out of any standard op-amp, but its a 
lot easier to use a part like an LM339, 

The pinouts for the chip are shown 
in Fig. 1 , and you should be struck by 
how much they look like op-amps. 
Just about the only pins that are 
missing are the ones for frequency 
compensation and offset adjust- 
ments. Those aren't needed in a 
comparator since the chip is de- 
signed to operate more like a switch 
than an op-amp. The gain is extremely 
high, the chip can be driven by a sin- 



A. At J 3 <? 









XL 



tz 



rz 



OUT 2. 


OUT 3 


H\ 


OUT / 


OUT 4- 


C- 


-/A/ / 


GA/D 


~7z\ 
~77 


+/N / 


-m4 


*i 


-/// Z 


-f-m 3 


? 


HN 2, 


—//V3 


3 







FIG. 1— THE LM339 VOLTAGE-comparator 
IC contains four comparators on the same 
substrate. We need only two comparators 
for a logic probe, so we'll have an extra 
pair. 



gle-ended supply, and the output can 
typically sink as much as 16 mA. 

The simplest circuit for a logic pro- 
be is shown in Fig. 2. As you can see, 
we've tied together two of the pins; 
one on each of the comparators. 
Those are the pins that are going to 
receive the input voltage from the 
probe. Since we want the output of 
both the high and low detectors to go 
high when they're turned on, we have 
to make the low detector inverting 
and set the high detector to be non- 
inverting. That's why we've con- 
nected the non-inverting input of IC1- 
a, the high detector, to the inverting 
input of ICl-b, the low detector, 

Now that we've decided where we 
want to put the input signal, the next 
step in the design is to work out the 
reference voltages that are going to 
be applied to the other input pins of 
the comparators. The easiest way to 
do that is by building a resistor volt- 
age divider — and that brings us to our 
first real problem. 

If we were going to use the logic 
probe only with CMOS, the design of 
the dividerwould be relatively simple. 
Since CMOS changes state halfway 
up the power rail, we could use two 
equal-value resistors for the divider. 
But that would seriously affect the 
versatility of the design so I'm onfy 
mentioning it as an aside. We have to 
do more than that because we also 
want it to be able to work with the 
standard TTL levels of below 0.8 volts 
for a low and above 2 volts for a high. 

The way to do that is to use three 
resistors in the divider chain, as 
shown in Fig. 2. By separating the 
high and low reference inputs of the 
comparators with a resistor, we can 
have our design account for the TTL 
deadband voltage range between 0.8 
and 2 volts. In Fig. 2, the output of 
IC1 -a will go high if the applied voltage 
at pin 6 is more than the reference 
voltage at pin 7, and the output of ICl - s 
b will go high if the applied voltage at ^ 
pin 5 is lower than the reference volt- ^ 
age at pin 4. J2 



75 



I 



R-E Engineering Admart 



Rates: Ads are 2!4"x2W. One insertion S995 each. Six insertions 5950 each. Twelve 
insertions $925 each. Closing date same as regular rate card. Send order with remittance to 
Engineering Admart, Radio-Electronics Magazine. 500-B Bi-County Blvd. , FarmingrJaie, NY 
11735. Direct telephone inquiries to Arline Rshman, area code-1-516-293-3000. FAX 
1-516-293-3115. Only 100% Engineering ads m accepted for litis Admart. 



FCC LICENSE 
PREPARATION 



The FCC has revised and updated the 
cornmercia! license exam. The NEW 
EXAM covers updated marine and 
aviation rules and regulations, 
transistor and digital circuitry. 
THE GENERAL RADfOTELEPHONE 
OPERATOR LICENSE - STUDY GUIDE 
contains vital information. VIDEO 
SEMINAR KITS ARE NOW AVAILABLE. 

WPT PUBLICATIONS 
979 Young Street, Suite E 
Woodburn, Oregon 97071 

Phone (503) 981-5159 Dept. 50 



MIDI 
PROJECTS 






BP182 — MIDI interfacing enables any so 
equipped instruments, regardless of the 
manufacturer, to be easily connected to- 
gether and used as a system with easy com- 
puter control of these music systems. 
Combine a computer and some MIDI instru- 
ments and you can have what is virtually a 
programmable orchestra. To get your copy 
send $5.95 plus SI .25 for shipping in the 
U.S. to Electronic Technology Today 
Inc., P.O. Box 240, Massapequa Park, 
NY 11762-0240. 



LINEAR IC EQUIVALENTS 
& PIN CONNECTIONS 



Linc.ir IC 
Equivalent* 
and Pin 

Connection!. 




BP141 — Shows equivalents & pin con- 
nections of a popular user-oriented 
selection of European, American and 
Japanese liner IC.'s 320 paaes, 8 x 10 
inches. $12.50 Plus $2.75 shipping. 
ELECTRONIC TECHNOLOGY TODAY 
INC., PO Box 240, Massapequa Park, 
New York 11762-0240. 






CIRCLE 186 ON FREE INFORMATION GARD 






CO 
O 

Z 

o 

DC 
H 
O 
UJ 

_i 

UJ 

6 

< 

or 



Now that we've got the basic con- 
figuration worked out, the next step 
is to calculate the values for the re- 
sistors. As we go through this, we'll 
be aiming for the 0.8- and 2-volt 
thresholds but, since we're going to 
be using standard-value resistors 
(things have to be cheap and avail- 
able, remember?), we'll probably 
miss the exact numbers by a little bit. 

Since we want the reference volt- 
age for IC1-a to be 2 volts (assuming 
a system voltage of 5 volts), we're 
aiming for a 3-volt drop across R1 — a 
final ratio of 3/5. That means the val- 
ue for R1 has to be 60% of the total 
value of R1+R2 + R3. Things are a 



more complex when we calculate the 
individual values for R2 and R3 since 
those two resistors don't see the 5- 
volt system voltage. The voltage divi- 
sion has to be based on the voltage 
appearing at pin 7 of ICl-a. 

Let's be a bit more rigorous about 
working this out. The voltage drop 
across the entire resistive chain is 
about equal to the system voltage. 
I'm saying "about" because there is a 
slight drop due to presence of the 
comparator, but the impedance of the 
inputs is so high that we can forget 
about it for all practical purposes. 
Since the three resistors are in se- 
ries, the sum of the voltage drops is 




r^cr/ 1 ^/? &?s/sroK 



FIG. 2— IN THIS LOGIC-PROBE CIRCUIT we've tied together one pin from each com- 
parator. Those pins will receive the input voltage from the probe. The low detector is 
inverting and the high detector is non-inverting. 



equal to the system voltage. 

Since we know that the voltage 
drop across R1 has to be 3V, the 
combined voltage drop across the 
other two resistors will be 2V. We 
also know that we want the drop 
across R3 to be 0.8V since that's the 
value of the reference voltage we're 
aiming toward. Some simple arith- 
metic tells us that the R2 drop has to 
be 1.2 V. 

Once we've taken the analysis this 
far, we've also calculated the relative 
values of the resistors. Since the re- 
sistors are in series, the same current 
is flowing through all of them and that 
means the resistor values are going 
to be directly proportional to the volt- 
age drops. R1 is going to be % of the 
total. R2 is going to be 1.2/5 of the 
total, and R3 is going to be 0,8/5 of 
the total. Putting things in simpler 
terms, if R T is the total value of the 
three resistors, R1 has to be 0.60R T , 
R2 has to be 0.24R T , and R3 has to 
be 0.1 6R T . 

Knowing the resistor ratios is only 
part of the answer since it's still short 
of knowing the actual values. In theo- 
ry, any combination of resistors in the 
correct ratio will work for us but there 
are some other things we have to 
take into consideration to come up 
with the final resistor values. 

When we get together next time, 
we'll take care of that, add a few sur- 
prises to the circuit, and get to talking 
about some other test gear you can 
build yourself. R-E 



76 




;1m|:|',:^J|,1'P 




Video standards 



JEFF HDLTZMAN 




ly first video terminal con- 
sisted of a 4800-baud 
I Micro Term terminal, with 
ASCII keyboard, driving a 5" Sony 
black-and-white portable TV, through 
a custom video interface suggested 
in a book by a guy named Don Lan- 
caster. Resolution was 16 lines by 64 
characters; needless to say, bit-map- 
ped graphics were not even a dream. 

Today, about 1 2 years later. I have a 
19" NEC MultiSync XL with a non- 
interlaced graphics resolution of 768 
lines x 1024 rows, in an essentially 
infinite variety of colors. 

What happened in the interim? And 
what's coming up next? 

Memory vs. I/O mapped 

Back in the early days of personal 
computers, user interaction was con- 
sidered peripheral to the main func- 
tion, computation. (By contrast, 
today some heretics believe that 
computation is peripheral to user in- 
teraction.) In line with that type of 
thinking, user input and output was 
handled a byte at a time, usually 
through an RS-232 interface that 
communicated with the CPU via a 
single I/O port. 

Of course, there were early excep- 
tions from Apple and Commodore. 
Those companies buitt memory-map- 
ped displays for the Apple II. the C64, 
and their successors. However, reso- 
lution was so low that sustained pro- 
fessional use produced eye strain. So 
most business machines centered 
around Z80's and serial ASCII termi- 
nals running under the CP/M operat- 
ing system. 

In August of 1981, IBM introduced 
its version of the personal computer. 
The IBM PC was based on a relatively 
new microprocessor, the 8088, that 
had 16 times the memory space of 
the Z80 machines prevalent at the 
time. 

In that seemingly boundless ad- 
dress space, IBM chose to imple- 
ment a memory-mapped video 
system, including both a character- 



based black-and-white system with 
resolution sufficient for sustained 
use in word processors, 
spreadsheets, and database man- 
agers, as well as a bit-mapped color 
system for entertainment. The two 
systems were assigned different 
memory addresses and I/O ports for 
control, so they could coexist in the 
same machine simultaneously, a fea- 
ture useful for programmers who use 
one screen for program output and 
the other for debugging. Some CAD 
systems also put drawings on one 
screen and menus on another. 

In one of the greatest ironies of this 
industry, and one that we continue to 
pay for every day even though the PC 
was designed with memory-mapped 
video hardware, IBM's BIOS imple- 
mented an interface that mimicked 
the old ASCII terminal approach. Per- 
formance was truly lousy; early PC 
word processors ran more slowly on 
a PC than via a 19,200-baud terminal. 

Programmers eventually devised 
more efficient interfaces to the video 
hardware, but created the problems 
of portability and compatibility that 
haunt us to this day, and that will con- 
tinue to haunt us until the PC archi- 
tecture has been laid to rest. But 
that's another story. 

Color and pixels 

The first bit-mapped graphics sys- 
tem for the PC was called the Color/ 
Graphics array, or CGA for short. In 
addition to several fuzzy text modes, 
CGA has two graphics modes: a 
"high-res" 640 X 200 in black and 
white, and a "low-res" 320 x 200 in 
four colors. (Table 1 summarizes im- 
portant video modes and resolu- 
tions.) The primary market for CGA 
adapters was game and educational 
software. 

Business users working in 1-2-3 
could display graphs on a CGA 
monitor, but not on the text-only 
monochrome display adapter (MDA). 
IBM missed a marketing opportunity 
and in stepped Hercules, whose 



monochrome graphics adapter quick- 
ly became a pseudo-standard whose 
reign lasted until very recently, when 
VGA became king of the hill. 

The Hercules card brilliantly solved 
several problems, including support 
of decent text-mode resolution, a 
separate graphics mode with resolu- 
tion exceeding that of the CGA, and 
the ability to work with standard 
monochrome monitors, which cost 
about 20-25% of CGA monitors at 
the time. 

But IBM did not sit still. In 1984, the 
company introduced the Enhanced 
Graphics Adapter (EGA), which 
maintained backward compatibility 
with the CGA, and added new text 
and graphics modes. The text mode 
ran in 16 colors, and had resolution 
sufficient for day-in and day-out 
usage. The new graphics modes al- 
lowed more colors (16) as well as 
more resolution (350 lines; columns 
remained constant at 640 pixels). Al- 
though still relatively expensive, the 
EGA proved that bit-mapped color 
displays could be useful for things 
other than arcade games. 

(For purposes of this discussion, 
I'm ignoring several IBM offerings 
that never took off, including the Pro- 
fessional Graphics Controller 
(PGC)J 

Then, in the spring of 1987, IBM 
introduced the PS/2 series, which in- 
cluded a new bus (the Micro Chan- 
nel), a new version of DOS (3.3), 
1.44MB floppy disks, and the next 
video standard, the Video Graphics 
Array (VGA). DOS 3.3 quickly be- 
came standard. It took a little longer, 
but eventually the new disk format 
became widespread. The jury is still 
out on the ultimate acceptance of the 
Micro Channel architecture. How- 
ever, in recent years VGA has taken 
off faster than a stream of electrons 
inside a CRT. VGA maintains com- 
patibility with CGA and EGA, and s 
adds several more higher-resolution ^ 
text and graphics modes. In addition, ^ 
from the beginning VGA included S 



77 



SELECT 5 BOOKS 
for only $4^ 



(values to $128.70) 
and get a FREE Gift! 



w 

o 
z 
o 

£E 
H 
O 



111 

g 

< 

DC 

78 




counW ■» 



Your most complete source for electronics books 

for over 25 years. 



An Absolutely No-Risk Guarantee 




Membership Benefits • Big Savings. En addition to 
this introductory offer, you keep saving substantially with 
members' prices of up to 50% off the publishers" 
prices. * Bonus Books. Starting immediately, you will be 
eligible for our Bonus Book Plan, wftti savings of up to 80% 
off publishers' prices. • Club News Bulletins. 15 times 
per year you will receive the Book Ctub News, describing 
all the current selections— mains, aiternates, extras — plus 
bonus offers and special sales, with scores of titles to 
choose from. • Automatic Order. If you want the Main 
Selection, do nothing and it wiil be sent to you automatical- 
ly. If you prefer another selection, or no book at all, simp- 
ly indicate your choice on the reply form provided. You wil) 
have at least 10 days to decide. As a member, you agree 
to purchase at least 3 books within the next 12 months 
and may resign at any time thereafter. » Ironclad No-Risk 
Guarantee. If not satisfied with your books, return them 
within 1 days without obligation! • Exceptional Quality. 
All books are quality publishers' editions especially 
selected by our Editorial Board. <Pu«BhM» pwh si»wn> 

All boons are hardcover unless number is followed by a "P" lor paperback. 
©1991 ELECTRONICS BOOK CLUB, Blue Ridge Summit. PA 17294-0810 



Blue Ridge Summit, PA 17294-0810 



D YES! Please accept my membership in the Electronics Book Club and send the 5 
volumes listed below, plus my FHEE copy of Delton T. Horn's All-Time Favorite Electronic 
Projects (3105P), billing me $4.95. If not satisfied, I may return the books within ten days 
without obligation and have my membership cancelled. I agree to purchase at least 3 books 
at regular Club prices during the next 12 months and may resign any time thereafter. A 
shipping/handling charge and sales tax will be added to all orders. 



Address 

City 

State 



Zip 



Phone 



Signature 

Valid 'or n«w members only Foreign applicants will rcce-ve special OfLterirsg iiiil rucliOrtS. Canada mutf remll m 
U.S. currency This -twdar aubjael lo occoplancs by the Ssclronies Book Club. RE591 



s 
5 



81 



TABLE 1— PC VIDEO MODES 


Mode 
NO.* 


Mode 
Type** 


Adapter*** 


Horiz. Res. 


Vert. Res. 


Max. 
Colors 





T/G 


CEVS 


40 


25 


16 


1 


T/G 


CEVS 


40 


25 


16 


2 


T/G 


CEVS 


80 


25 


16 


3 


T/G 


CEVS 


80 


25 


16 


4 


G 


CEVS 


320 


200 


4 


5 


G 


CEVS 


320 


200 


4 


6 


G 


CEVS 


640 


200 


2 


7 


T 


CEVSHM 


80 


25 


2 


D 


G 


EVS 


320 


200 


16 


E 


G 


EVS 


640 


200 


16 


F 


G 


EVS 


640 


350 


2 


10 


G 


E/VS 


640 


350 


4/16 


11 


G 


VS 


640 


480 


2 


12 


G 


VS 


640 


480 


16 














13 


G 


VS 


320 


200 


256 


6A 


G 


s 


800 


600 


16 


100 


G 


s 


640 


400 


256 


101 


G 


s 


640 


480 


256 


102 


G 


s 


800 


600 


16 


103 


G 


s 


800 


600 


256 


104 


G 


s 


1024 


768 


16 


105 


G 


s 


1024 


768 


256 


106 


G 


s 


1280 


1024 


16 


107 


G 


s 


1280 


1024 


256 


In hex 
" T = Te> 
*•« c = cc 


idecimal 

:t only, G = Graphics only, T 

SA, E=EGA, V=YGA S= 


/G - Bit- mapped text 

Super VGA, M = MDA, H = Her 


cules 



w 
o 

z 
o 

DC 
h- 

o 
w 

_i 
uj 

6 

Q 
< 



built-in gray-scaling capabilities, so 
you can plug either a monochrome or 
a color monitor into a given adapter, 
and your software will run un- 
changed. 

Beyond VGA 

VGA is nice, but it's not the end of 
the story. As soon as IBM introduces 
a product to the PC market, other 
vendors quickly seek to improve it, 
and VGA was no exception. Third- 
party vendors quickly pushed resolu- 
tion up to 800 x 600, 1024 x 768, 
and other intermediate resolutions. 
At first, each vendor implemented its 
hardware and software in different 
ways. Soon, however, the industry re- 
alized it was headed for chaos, so the 
Video Electronics Standards Associ- 
ation (VESA) formed to define stan- 
dards for beyond-VGA modes, VESA 
membership includes virtually all 
manufacturers of monitors and video 
adapters — except IBM, Hercules. 
Compaq, and a few others. 

What VESA has done is stan- 



dardize horizontal and vertical sweep 
frequencies, and assign BIOS mode 
numbers for standard resolutions, as 
shown in the bottom half of Table 1 . 
These standards should make it easi- 
er to write software drivers and as- 
sure customers of compatibility. 

Beyond Super VGA 

Super VGA is really nice — but it's 
not the end of the story either. The 
reason is that the VGA architecture is 
dumb, dumb, dumb. It requires the 
host CPU to do all of its bit twiddling. 
To draw a line, the host CPU must 
write directly to memory, often a sin- 
gle memory location for each af- 
fected pixel. At low resolution, 
performance may not be affected 
much by letting the host CPU do ev- 
erything. But as resolution increases, 
the host CPU must spend an increas- 
ing proportion of its time tending to 
the screen, which slows down the 
rest of the system. 

Wouldn't it be nice if the host CPU 
could delegate some responsibility 



and free itself up for other types of 
tasks? Well, it can. The trick is to put 
some intelligence on the video adapt- 
er card itself. Then the host CPU can 
tell it, "Draw a line from 0<1, YD to 
(X2.Y2), and let me know when 
you're done," and meanwhile go on 
and do something else like tend to a 
background print spooler, recalculate 
a spreadsheet, reformat or spell- 
check a document, or accept charac- 
ters from a modem. 

IBM's first entry in the world of 
intelligent graphics adapters was the 
851 4/A, introduced shortly after the 
VGA in 1987. Unfortunately Cfor 
IBM), the company shrouded the 
8514/A in a veil of secrecy by not 
publishing hardware-level specs, as 
the company had for all previous 
adapters. So third-party vendors had 
to reverse-engineer on -board IC's, 
which slowed development of clones 
and software support, hence accep- 
tance in the market. In addition, the 
8514/A is really a half-breed that pro- 
vides only partially intelligent control 
over the video buffer. Further, IBM's 
8514/A produces an interlaced dis- 
play that many people (including me) 
find visually straining. The main justi- 
fication for interlaced monitors is that 
they are slower, hence cheaper, than 
non-interlaced monitors. Although 
the 8514/A provides comparable res- 
olution and better performance than 
the better Super VGA boards, it 
seems unlikely that it will ever attain 
the importance of VGA. 

Beyond beyond-Super-VGA 

While IBM floundered, Texas In- 
struments released the 34010 graph- 
ics coprocessor and a robust, 
general-purpose software interface 
to it. The 34010 is a full-fledged mi- 
croprocessor with a powerful instruc- 
tion set containing many graphics- 
specific commands. At first, support 
for the 34010 was sparse, but with 
the increasing popularity of graphical 
user interfaces, support is increas- 
ing, competition is heating up, and 
board prices are falling. (See the 
sidebar for a discussion of Hercules' 
new 34010 board.) 

Of course, IBM doesn't give up 
without a fight. In the fall of 1990, Big 
Blue introduced its next-generation 
video controller, the Extended Graph- 
ics Array CXGA). XGA differs from 
8514/A in several significant re- 
spects. First, it's 100% VGA-com- 
patible. Second, it's more intelligent 



82 



R-E Computer Admart 



GETTING 
THE MOST 
FROM YOUR 
PRINTER 



Getting The 
Mo*t From Your 
Printer 




BP181— It is probable that 80% of dot-ma- 
trix printer users only ever use 20% of the 
features offered by their printers. This book 
will help you unlock the special features and 
capabilities that you probably don't even 
know exist. To order your copy send $6.95 
plus St. 50 for shipping in the U.S. to Elec- 
tronic Technology Today Inc., P.O. Box 
240, Massapequa Park, NY 11762-0240. 



Rates: Ads are 2K"x2%". One insertion S995 each. Six insertions $950 each. Twelve 
insertions 5925 each. Closing date same as regular rate card Send order with remittance to 
Computer Admart, Radio-Electronics Magazine, 50Q-B Bi-County Blvd., Farmingdale, NY 
11735. Direct telephone inquiries to Ariine Fishman, area code-1 -516-293-3000. FAX 
1-516-293-3115. Only 100% Computer ads are accepted (or this Admart. 



| ICs 


PROMPT DELIVERY!!!! 


SAME DAY SHIPPING (USUALLY) 


OUANTTTY OME PUCES SHOWW 10* WAR. J. 1 »1 1 




DYNAMIC RAM 


K^l iM Bnnrrt Inr nn 1 .1 


Hire 


S160.00K s 


IflSIMV 


4Mx9 


80 ns 


240.00 m ~ 


Bd3 SIMM 


1Ml9 


60 ns 


63.00 p : 


■ga simw 


(Mx9 


80 ns 


54.00 P 1 


H 4 Mbit 4Mx1 


80 ns 


3000 E i 


HI'- Mbit 


80 ns 


4s.no m ' 


KM1 Mbit 


80 ns 


5.75 m - 


RE>412S6 


256Kx1 


100 ns 


2.I0B 1 


94125C 


256Kx1 


120 ns 


l.9Spi 


■ 442 5« 


256K*l 


100 ns 


s.gs m j 


H44S4 


64Kx4 


100 ns 


1 .95 m i 




EPROM 


■P 


P|sl27C4001 512KXS 


150 ns 


$55.00 I* 


■^S27C1000 i.'BK.f: 


150 ns 


16.50 pfc 


■ 27C512 64Kxa 


120 ns 


7.50 ■ 


9 2725I 


32Kx8 


150 ns 


5.00 ■ 


*J27128 


250 ns 


3.40 ■ 




STATIC RAM 




■•£■ 1 Mbit £'£:-:■ :l: 


100 ns 


sis.ool 


BililG2256LP 


100 ns 


6.50fl 


I OPEN 6' i QA 


ys.7» 


tu 10 r 


i SMPVIAFEOEXONSAT 1 


1 SAT DEL OH 


WflSlcrCirrJ VIS. 


A Of UPS CA- 


3MCOO 


1 FEt-ES OflOfiflS 


MICROPROCESSORS 


JNUMITED. INC 


1 r; ! ;: f ,i p Bit 


LaaSesirflfl«"s , :>', ^ 


1 fr. M 1:TX 1 k 


No minimum §t&6i- p>uia -tw 




1 COO AVAIL ABLE 


Ihfpnj ■ru^ino* 







PT68K4 

68000-16MHZ 
*EGA/VGA* 

*fflGH DENSITY DRIVES* 

• 4 MB of onboard DRAM 

• 4 RS232 + 2 Parallel Ports 

• Floppy Disk Controller 

• 7 XT Expansion Slots 

16 MHZ Kits from $189 

Assembled Boards from $499 
Professional OS9/68000 $299 
Peripheral Technology 

1480 Terrell Mill Rd. Suite 870 

Marietta, GA 30067 

404/984-0742 




CIRCLE 61 ON FREE INFORMATION CARD 



CIRCLE 189 ON FREE INFORMATION CARD 



than the 8514/A, so it should be fast- 
er. Third, it runs only on Micro Chan- 
nel PS/2's, which limits its potential 
market. Fourth, it requires a 386 or 
486 to run, which also limits its poten- 
tial market. Fifth, like the 8514/A, the 
XGA produces an interlaced display, 
so it's subject to flicker. 

At present it's hard to see, given 
the falling prices of 34010 boards, 
how the XGA is going to have any 
significant impact on the market. CFor 
a technical overview of the XGA, see 
Jake Richter's article in the February 
issue of Byte.) 

Color and resolution 

In this discussion so far, I've mostly 
ignored the issue of color. CGA al- 
lowed a maximum of four in its low-res 
mode: EGA increased the maximum 
to 16; and VGA increased the max- 
imum to 256, but with that many col- 
ors the resolution dropped back to 
the low-res CGA level. (Even so, 256- 
color images at that resolution are 
much more realistic than 16-co!or im- 
ages at much higher resolutions.) In 
the meantime, the Super VGA 
boards developed support for 256 
colors at all resolutions up to 1024 x 
768. 

256 colors are nice— but it really 
takes about 16 million C2 24 ) colors for 
true photo-realistic imaging. Special 
workstations have had that type of 
imaging for awhile, as have high-end 
Macintoshes. But now these "true- 
color" boards are drifting over to the 



HERCULES' GRAPHICS 
STATION CARD 

You can sum up the 34010-based 
Hercules Graphics Station card in 
three words: speed, speed, speed. I 
tested it in a 33-MHz 386 under Win- 
dows 3.0, and it roughly doubled 
screen redraw speed. For example, 
Word for Windows ran about as fast 
as a text-mode word processor under 
DOS. The card provides lull hard- 
ware-level VGA emulation, a 512 x 
480 true-color mode, and a 1024 x 
768 256-color mode. Sample true- 
color images included with the board 
are breathtaking. The board is well- 
built, and comes with drivers for Win- 
dows 3.0, AutoCAD 11, and others. 

Installation and documentation are 
a bit rough, and I encountered the 
rudest technical-support person I've 
run across in years while ironing out a 
driver upgrade problem. But after 
overcoming those hurdles, I really 
enjoyed using the Hercules Graphics 
Station Card. It really puts some zing 
into Windows, and the company ex- 
pects to improve performance as 
Windows learns how to take advan- 
tage of intelligent graphics sub- 
systems. 

Tfie card lists for about $1000, but 
is available through mail-order chan- 
nels for about $700. Highly recom- 
mended for heavy Windows and 
AutoCAD users. Hercules Computer 
Technology, Inc., 921 Parker Street, 
Berkeley, CA 94710. (415) 540-6000. 

CIRCLE 41 ON FREE INFORMATION CARD 



PC environment. However, they're 
very expensive ($4000 and up). 

What's ahead 

HDTV continues to loom just 
beyond the horizon. In terms of the 
way I spend my time, I don't much 
care about it for entertainment, but I 
do care about it in the way it could 
affect computer- monitor pricing if the 
technologies converged. The least- 
expensive 19" 1024 x 768 monitors 
now go for about $1500. but if the 
same technology were used in HDTV 
displays, that price could easily drop 
by two thirds. Of course, a strong 
U.S. presence in HDTV would do 
much for our economy, the trade defi- 
cit, semiconductor manufacturing,... 
you name it. Let's hear it for a strong 
U.S. presence in HDTV! 

What to buy 

There is no reason not to buy VGA. 
During the past year the price of a 
plain VGA adapter card has dropped 
to about $100, and monochrome 
VGA monitors are available for under 
$150. Color VGA monitors now go 
for about $350, SuperVGA monitors 
for about $500, and Super VGA 
board/monitor combinations can 
also be had for about $500. Bought 
as part of a system, color VGA typ- 
ically adds about $300 to the overall 
cost. Don't buy anything less than ^ 
monochrome VGA. and if you run $ 
Windows, aim for 800 x 600 Super £ 
VGA as a minimum. R-E S 



83 



MARKET CENTER 



FOR SALE 



w 
o 
z 

O 

DC 
F 
O 

LU 
_1 
ID 

6 

a 
< 

en 



84 



FREE cable and satellite descrambler plans. Send 
self addressed stamped envelope. MJM INDUS- 
TRY, Box 531, Bronx, NY 10461-0208. 

TUBES; "oldest," "latest." Parts, and schematics. 
SASE for lists. STEINMETZ, 7519 Maplewood Ave., 
RE, Hammond, IN 46324. 

ENGINEERING software, PC/MSDOS. Hob- 
byists — students — engineers. Circuit de- 
sign and drawing, PCB layout, Logic 
simulation, FFT analysis, Mathematics, Cir- 
cuit analysis. Call or write for free catalog. 1 
(800) 728-3805, BS0FT SOFTWARE, 444 
Colton Rd., Columbus, OH 43207. 

RESTRICTED technical information: Electronic sur- 
veillance, schematics, locksmithing, covert sci- 
ences, hacking, etc. Huge selection. Free 
brochures. MENTOR-Z. Drawer 1549. Asbury 
Park, N J 07712. 



I'LL HAVE MINE 
DESCRAMBLED 




If you find a better deal, We'll beat 
It! JERROLD • TOCOM • HAMLIN • 

OAK • SCIENTIFIC ATLANTA • 

ZENITH • ask about our warranty 

program C.O.D. Visa, M/aAM.EX. 

welcome. FREE CATALOG 

• FREE CALL 

•OPEN SATURDAYS 

1 800 562-6884 

VIDEO TECH 

3702 S. Virginia St. Ste. 160-304 

Reno, NV 89503 



CABLE TV converters: Jerrold, Oak, Scientific At- 
lantic, Zenith & many others. "New MTS" stereo 
add-on: mute & volume. Ideal for 400 and 450 
owners! 1 (800) 826-7623, Amex, Visa, M/C accept- 
ed. B & B INC., 4030 Beau-D-Rue Drive. Eagan, 
MN 55122. 

TUBES, new, up to 90% off, SASE, KIRBY, 298 
West Carmel Drive, Carmel, IN 46032. 



FREE CATALOG 



FAMOUS "FIRESTIK" BRAND CB ANTENNAS 

AND ACCESSORIES. QUALITY PRODUCTS 

FOR THE SERIOUS CB'er. SINCE 1962 



FIRESTIK ANTENNA COMPANY 

2614 EAST ADAMS 

PHOENIX, ARIZONA 85034 



TOCOM VIP converters w remotes from $299.00. 
TOCOM PREMIUM SUPER CHIPS from $49.00 
turn on everything, guaranteed. Phone (219) 
935-4128, evenings 6-12PM EST. 

YOU can find anyone! Obtain confidential postal 
and DMV records, birth/death, credit, etc. S17.95. 
PSSST PRODUCTS, Box 2501. Huntington Beach, 
CA 92647. 



TOCOM VIP converters w/remote from $279.00. 
Tocom super chips lurn on everything, $49.00 each. 
Phone (219) 935-4128. 



FM 2-way, CB-amateur. scanners, radar detec- 
tors, auto alarms, catalog $2.00, RAYS, PO Box 
14862, Fort Worth, TX 76117. 



CLASSIFIED AD ORDER FORM 

To run your own classified ad, put one word on each of the lines below and send this form along with your check to : 

Radio-Electronics Classified Ads, 500-B Bi-County Boulevard, Farmingdale. NY 11735 

PLEASE INDICATE in which category of classified advertising you wish your ad to appear. For 

special headings, there is a surcharge of $25.00. 

( I Plans/Kits ( ) Business Opportunities ( ) For Sale 

j Education/ Instruction ( ) Wanted { ) Satellite Television 

Special Category: $25,00 

PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS. 

(No refunds or credits for typesetting errors can be made unless you clearly print or type your 
copy.) Rates indicated are for standard style classified ads only. See below for additional 
charges for special ads. Minimum: 15 words. 



10 



11 



12 



13 



14 



15 ($46.50) 



16 ($49.60) 



17 ($52.70) 



18 ($55.80) 



19 ($58.90) 20 ($62.00) 



21 ($65.10) 22 ($68.20) 23 ($71.30) 24(574.40) 



25 ($77.50) 



26 ($80.60) 27 ($83.70) 28 ($86.80) 29 ($89.90) 30 ($93.00) 



31 ($96.10) 32 ($99.20) 33 ($102.30) 34 ($105.40) 35 ($108.50) 

We accept MasterCard and Visa for payment of orders. If you wish to use your credit card to pay tor your ad fill 
In the following additional information (Sorry, no telephone orders can be accepted.): 



Card Number 



Expiration Date 



Please Print Name 



Signature 



IF YOU USE A BOX NUMBER YOU MUST INCLUDE YOUR PERMANENT ADDRESS AND PHONE 
NUMBER FOR OUR FILES. ADS SUBMITTED WITHOUT THIS INFORMATION WILL NOT BE ACCEPTED. 
CLASSIFIED COMMERCIAL RATE: (for firms or individuals offering commercial products or services) 
$3.10 per word prepaid (no charge for zip code)... MINIMUM 15 WORDS. 5% discount for same ad in 6 
issues; 10% discount for same ad in 12 issues within one year; if prepaid. NON-COMMERCIAL RATE: (for 
individuals who want to buy or sell a personal item) $2.50 per word, prepaid....no minimum. ONLY FIRST 
WORD AND NAME set in bold caps at no extra charge. Additional bold face (not available as all caps] 55c 
per word additional. Entire ad in boldface, $3,70 per word. TINT SCREEN BEHIND ENTIRE AD: S3.85 per 
word. TINT SCREEN BEHIND ENTIRE AD PLUS ALL BOLD FACE AD: $4.50 per word. EXPANDED 
TYPE AD: S4.70 per word prepaid. Entire ad in boldface. $5.60 per word. TINT SCREEN BEHIND ENTIRE 
EXPANDED TYPE AD: $5.90 per word TINT SCREEN BEHIND ENTIRE EXPANDED TYPE AD PLUS 
ALL BOLD FACE AD: $6 80 per word, DISPLAY ADS: 1" X 2W— $410,00; 2" x 2W— $820.00; 3" x 
2W" — $1230.00. General Information: Frequf ,cy rates and prepayment discounts are available. ALL 
COPY SUBJECTTO PUBLISHERS APPROW „ ADVERTISEMENTS USING P.O. BOX ADDRESS WILL 
NOT BE ACCEPTED UNTIL ADVERTISER SUPPLIES PUBLISHER WITH PERMANENT ADDRESS 
AND PHONE NUMBER. Copy to be in our hands on the 5lh of the third month preceding the date of Ihe 
issue, (i.e., Aug. issue copy must be received by May 5th). When normal closing date falls on Saturday, 
Sunday or Holiday, issue closes on preceding working day. Send for the classified brochure. Circle Number 
49 on the Free Information Card. 



WIRELESS CABLE RECEIVERS 1,9 TO 2.7 GHz 



C 



30 CH PAfiABOlIC OISH SVSTtM 1173 90 
30 CH ROD ANTENNA SYSTEM $193 40 

30 CH CIWSTAL CONTROIKO SYSTEM SJ94 95 

sum ncnowtvE ink. iwc send si a for 

f a s ra i uk: cut* log OK THESE 

PHOENIX. U. SS067 UNO OTHER FINE 

(S0!| J3O-DH0 VIDEO PRO DUCTS 

OUHRIITI DISCOUNTS 



TEST equipment p re-owned now at affordable 

prices. Signal generators from $50.00, os- 
cilloscopes Tram $50.00, other equipment, including 
manuals available. Send $2.00 U.S. for catalog, 
refunded on 1st order. J.B. ELECTRONICS, 3446 
Dempster, Skokie. IL 60076. (706) 982-1973. 

CABLE TV converters & descramblers for Jer- 
rold and Scientific Atlanta. Low prices, one year 
warranty. We Ship COD. BAY STATE ELEC- 
TRONICS, PO Box 103, Boston, MA 02188. 1 (800) 
359-9806. 

CAR stereos, equalizers, amplifiers, speakers, 
woofers, tweeters, speaker box supplies, alarms, 
DJ mixers, more. Large catalog $1.00. ELEC- 
TRISONIC-K1 , 8400 Alameda, El Paso, TX 79907. 



ANTIQUE RADIO CLASSIFIED 
Free Sample! 

Antique Radio's *■ 

Largest Circulation Monthly. ( Bf®J 
Articles. Ads & Classifieds. 
6-Monttt Trial: $13. 1-Yr: $24 {$36-1 st Class). 
A.R.C., P.O. Box BDE-L6, Carlisle, MA 01741 




DISCOUNT computer books: Thousands of titles 
available. Including recent releases. Please call or 
write for our free catalog. BO OK WARE, 344 Water- 
town Road, Thomaston, CT 06787. 1 (800) 
288-5662. (203) 283-6973. 

STOP prank phone calls Electronic device dis- 
plays phone number of person calling you, $89.95 
[assembled), brochure $1.00, surveillance catalog, 
$5.00, EDE, POB 337, Buffalo, NY 14226- 

CABLE descramblers, new X-12 Oak descrambler 
CH-2-3 $49 0O 10-$39.00 2O-S29.0O, Oak RTC-56 
CH-2-3 with remote $125.00 10-$115.00 
20-$100.00, M-35-B $49.00 10-$39.00 20-$23.00. 
Tocom 5503 w/r $199,00 10-$189.Q0 20-$1 75.00, 
SYL 4040 replaces Jerrold 400-DtC w/r $125.00 
10-S1 00.00 2O-S75.00, 4040 with internal tri-bi su- 
perfast w/r $165.00 10-$150,00 20-S125.00 with in- 
ternal S-A descrambler $165.00 10-$150.00 
20-$125.00, with internal Hamlin descrambler 
$125.00 10-$100.O0 20-$75.00. MLD-1200, SA3B, 
Super-Tri-Si, same low prices. Zenith Z-TAC 
$225.00 COD. OK MOUNT HOOD ELEC- 
TRONICS (503) 253-0459. 

DESCRAMBLERS, wholesale prices, examples 
X-12 Oak descrambler $49.00, RTC-56 combo 
$135.00, Tocom 5503 combo $199.00, 4040 SB 
combo $125.00 S.A.C., info (702) 647-3799, Orders 
1 (800) 622-3799. 



' Quality Microwave TV Antennas 



WIRELESS CABLE ■ IFTS - MMDS ■ hiuleur TV 
Ultra Hrgh Gain 5M>(+) • TiMibU 1.9 la 2.7 Ghi. 

• 36-Channd System Complete $149.95 

• '2 -Channel System Complete S1 14.95 

• Call or write (SASE1 for "FREE" Catalog, 
PHILLIPS-TECH ELECTRONICS 
P.O. Box 3533 • ScDttsdile, AZ 85252 

£ (E02) 947-7700 |$3.00 Credit all plniieordEril 
WARRANTY .MaileiCard * Vlii ■ COD'i • Uaantity Pricing 



PARTS at bargain prices. Free flyer: NETWORK 
SALES, 90 Turner, Elk Grove. IL 60007. (708) 
952-1115. 

SECRETS of data encryption standard $7,00, se- 
cure microprocessors explained $5.00, "smart 
cards" explained $5.00. Details free. Sent first class. 
BBB, Box 637, Polk City, FL 33668. 

ADULT video tapes 90 min. VHS current color vid- 
eos assorted titles 1 — $10.00 3 — $25.00. Free 
shipping. STRINGSOFT, Box 915-R. Old Bridge, NJ 
08857. 



CABLE TV converters and descramblers. 
We sell only the best. Low prices. SB-3 
$79.00. We ship C.O.D. Free catalog. ACE 
PRODUCTS, PQ Box 582. Dept. E. Saco. ME 
04072. 1 (800) 234-0726. 

PR I N TE D circu it board s etched & d ri I led . Free deliv- 
ery. K& F ELECTRONICS, INC., 33041 Groesbeck, 
Fraser, Ml 48026. (313) 294-8720. 

CABLE descramblers (Jerrold) from $40.00. Tocom 
VIP test chip. Fully activates unit. Also Zenilh lest 
board. Fully activates Z-Tacs. $50.00. Call (213) 
867-0081. 

TV. notch filters, phone recording equipment, bro-. 
chure $1,00. MICRO THinc, Box 63/6025. Mar- 
gate. FL 33063. (305) 752-9202. 



CB RADIO OWNERS! 



We specialize in a wide variety of technical 
information, parts and services for CB radios. 
10-Meter and FM conversion kits, repair books, 
plans, high-performance accessories. Thousands 
of satisfied customers since 1976! Catalog $2. 



CBC INTERNATIONAL 

P.O. BOX 31500RE. PHOENIX, AZ 85046 



TECHNICIANS. The ultimate tesl lead, jumper ca- 
bles with switch $1 4.95 each. MHA, PO Box 152797. 
San Diego, CA 92195. 

INFRARED remote controlled RF and A/V 
switches. Write or call to order or get additional 
information about Infracon's complete MediaMaster 
series of infrared conlrolled switches: MediaMAster 
RF-5X2 and MediaMAster AV-4X4. INFRACON, 
PO Box 1205, Richardson, TX 75085-1205. (214) 
437-3366. 

PHOTOFACT folders under #1400 $5.00. Others 
$7.00. Postpaid. LOEB, 414 Chestnul Lane, East 
Meadow, NY 11554. 



Try the 

trhujlrtiniris 

bulletin board 
system 

(RE-BBS) 
516-293-2283 



The mare you use it the 
more useful it becomes. 

We support 300 and 1200 
baud operation. 

Parameters: 8N1 (8 data 
bits, no parity, 1 stop bit) 
or 7E1 (7 data bits, even 
parity, 1 slop bit). 

Add yourself lo our user 
Files to increase your 
access. 

Communicate with other 
RE readers. 

Leave your comments on 
RE with the SYSOP. 



RE-BBS 
516-293-2283 



CABLE TV DESCRAMBLERS! 
BARGAIN HEADQUARTERS! 



•JERROLD 1 " 'TOCOM -HAMLIN 

•OAK 'ZENITH 

• SCIENTIFIC ATLANTA 

6 month warranty! We ship COD! 
Lowest retail/wholesale prices! 

FREE CATALOQ: 

Global Cable Network 

1032 Irving St. Suite 109 

S.F., CA 94122 
NO CALIFORNIA SALES!!! 

ORDER TODAY! 800-327-8544 



CABLE TV 

DESCRAMBLER LIQUIDATION! 



FREE CATALOG! 

Hamllo Combos S44. Oak W35B $60 (mln. 5), etc. 



WEST COAST ELECTRONICS 

For Information: 818-709-1758 

Catalogs & Orders: 800-628-9656 



THIS IS A BOLDFACE EXPANDED AD. IF you 
like this format the cost is 55.65 per word. 



CABLE TV 



TB-3 (Tri-Bi) or SA-3 

Quantity Prices 



10 



20 



$48. $43 



Each 



50 



Each 



100 



5pjy H 3>*50i 



Each 



Each 



Hours open 10:00 am to 4:00 pm Eastern time 

Minimum order 5 units 55.00 ea. 

Dealers wanted. We ship COD. 

King Wholesale 

1-800-729-0036 

Fax number 6173400053 

'Wo one beats the King's prices!" 



DESCRAMBLERS 



5 



85 



Cable Descramblers 



New Auto Tri-Bi guaranteed no flashing $165,00 

SB-J ..,_. S99.00 ZENITH SUPER 

TRIMODE SIO9.0O SAAVI........ S19SUX) 

11AMLIN ......... S99.00 TOCOM _. J319.O0 

SCIENTIFIC- EAGLE J119.00 

ATLANTA S 119.00 COPY GUARD $59.95 

OAK M35B... SW.OO STARGATE 2000... 188,00 

ZENITH 1175.00 

M.D. Electronics will match or beat any 
advertised wholesale or retail price. 



Your best buys and warranties for 
table converters and d esc ramblers 
start with a FREE catalog from VI D 



EXCELLERATOR 

CABLE CONVERTERS 
WHEN QUALITY COUNTS 




For Information Call 

402-554-0417 

To order or request a free catalog 

1-800-624-1150 



New Dynatrack™ fine tuning provides unmatched picture quality 

550 MHz inner provides 83 channel capacity 

Sleep timer for Automatic shut off within 1 5-90 minutes 

213 switthabl* IIRC / IRC / Standard Switchable 

2 Year warranty, Last channel recall. Favorite channel select, Scan 

Double vented high efficiency transformer far coot performance 

Stargate-2001 $99.00 

Siargate-550XL SI 19.00 With Volume Control 

Don't settle for anything less. 



Oj- xC> Om*h*t NEOOIl4 ATJ^s:x>COMJ^YWOtALL5rrV77i^^ 

*(&■• j* g&fbT OWNHBJHFOF CAHJ TV EQUITHGT. EF TOU AM UNSURE OF TH1SK LAWS 



B c.o.n. 



CHECK wmt VOL"* LOCAL OfFK'rAU 



CIRCLE 53 ON FREE INFORMATION CARD 



RADIO tubes. Scarce new. used. Extensive listings. 
Capacitors, etc. Illustrated flyer $1.00 (deductable). 
DIERS, 4276-E7 North 50th Street, Milwaukee, Wl 
53216-1313. 

CABLE TV descramblers wholesale DRX — 3 DIC 
with remote $60.00 each for 20 pieces. CHICAGO 
CABLE VIDEO, 923 South Main Street, Algonquin. 
IL 60102. 1 (800) 442-9653. No Illinois orders. 






CODE SCANNER 

Compact unit copies Morse, RTTY, ASCII 
codes from your radio on 32 character 
LCD display. Ten day money back. 

Model CSCAN $1S9,0O+S5 S&H 

MICROCRAFT P.O. Box 513R 

Thiensville, Wl 53092 

Telephone (414) 241-8144 



REMOTE CONTROL. KEXCHAIN 

... Complete w/mini-tfansmiUBf . 

• and +5 vdc RF receiver ■'■: 
Fully aaoembfed including plans 
. .to build your own auto alarm.:. 
: ::;:. QuanOly die counts a. vatlable : !;: 

rt%A« rtr Check;vis*or MfC:o 
<>ii4.y0 Add $ 3 shipping 

VISITECT INC. BOX 5442, SO.SAN FPAN.^ CA. 34GM 

i;-(41 5) 872-0128 :- V: Fax (415) 872-2635 




PCB and schemata CAD software. Easy multilayer 
rubberband zoom pan and more. CGA EGA IBM 
compatibles, S195.00. NUMBER ONE SYSTEMS. 
10565 Bluebird Street, Coon Rapids, MN 55433. 
Demo Disc. (612) 757-8584. 

SURVEILLANCE — Audio/video.'infra-red.'laser 
equipment. Industrial or private. 500 ilem catalog 
$7.00. SECURITY SYSTEMS, 3017G Hudson, 
New Orleans, LA 70131. 



PLANS AND KITS 



y 
z 

O 
CC 
F- 
O 



ID 

g 
o 
< 



CATALOG: hobby/broadcasting/HAM.CB: Cable 
TV, transmitters, amplifiers, surveillance devices, 
computers, more! PANAXIS, Box 130-F5, Para- 
dise, CA 95967. 

DAZER ll personal protection device! Plans $8.00. 
Lasers! Transmitters! Detectors! More! Kits or as- 
sembled! Catalog $2.00. QUANTUM RESEARCH, 
16645-113 Avenue, Edmonton, Alberta T5M 2X2. 

DESCRAMBLING, new secret manual. Build your 
own descramblers for cable and subscription TV. 

Instructions, schematics for SSAVI, gated sync, 
sinewave. (HBO, Cinemax, Showtime, UHF, adult) 
$12.95, $2.00 postage. CABLETRONICS, Box 
30502, Bethesda, MD 20824. 

HOW TO use surface mount techniques. Build ultra 
miniature projects. Included free, two sets plans. 
Infra red remote control, and light display. Send 
$15.00 to CHARLIE'S VIDEO, Depl. SMT, PO Box 
7782, LaSierra, CA 92503. 



DIGITAL V.O.M./D.RM. 
SALES— SERVICE— PARTS 



FLUKE-BECKMAN-SIMPSON-ETC. 

U S. MADE ONLY. QUOTATION PRIOR TO WORK. FAST 
SERVICE, 90 DAY WARRANTY. STANDARDS 
TRACEABLE TO NBS. SINCE 1948. CALIBRATION 
CERTIFICATE AVAILABLE. 

INDUSTRIAL INSTRUMENT WKS. INC. 
5745 SALMEN , HARAHAN , LA 70 1 13 504,733-8355 



CONTROL timing plans: 3 designs for programma- 
ble control of relays, power supplies, and more. 
$8,95 Free info. RON DAY, 1625 Kirkwood Dr., 
Garland, TX 75041. 

ROBOTICS! Engines! Inventions! Muscle wires 
contract with surprising strength when powered. 
Send business SASE for latest flyer. MONDO-TRO- 
NICS Co RE, 2476 Verna Ct„ San Leandro, CA 
94577. 



HYPNOTIZE or Relax electronically! Alpha/medita- 
tion goggles. Complete kit $53.00. Free information 
MARK WORLEY, Box 261113, San Diego, CA 
92196. 

SURVEILLANCE transmitter kits! Four models of 
each; telephone, room, combination telephone/ 
room transmitters tune from 65 to 305 MHz. Catalog 
with Popular Communications and Popular 
Electronics book reviews of "Electronic Eaves- 
dropping Equipment Design," $2.00. 
SHEFFIELD ELECTRONICS, 7223 Stony Island 
Ave.. Chicago, IL 60649-2806. 

POWERFUL single-chip FM voice transmitter, size 
of a postage stamp, transmits to any FM radio up to 
one mile away. Complete kit S13.95 postpaid. 
HERTZ MICRODEVICES, Box 41771-B, LA. CA 
90041-41771. 

SURVEILLANCE electronics, plans, kits, as- 
sembled. Calalog $4.00. S & S ELECTRONICS, 
PO Box 36505-1 23E, SanJose, CA 95158. 

AUDIO! Plans/products — inexpensive, profession- 
al, amps, mixers, more! Literature/cassette — 
$3.00! DAVISOUND, Box 521, Newberry. SC 29108. 



CABLE DESCRAMBLERS 
OAK M35B COMBO $39.35 



Jerrold, Zenith, Hamlin, Sci. Atlanta, Pioneer 

& MORE! OUR PRICES ARE BELOW WHOLESALE! 

CABLE-H PLUS 

14417 Chase St. #481-A Panorama City, CA 91402 

1-800-822-9955 • Other Info. 1-818-785-4500 

NO CALIF. SALES - DEALERS WANTED 



SATELLITE TV 



FREE catalog — Lowest prices worldwide, save 40 
— 60%. Systems, upgrades, parts, ail major brands 
factory fresh and warrantied. SKYVIStON, 2009 
Coltegeway, Fergus Falls, MN 56537. 1 (800) 
334-6455. __ 

VIDEOCYPHER II descrambttng manual. Sche- 
matics, video and audio. Explains DES, Eprom, 
Clonemaster, 3Musketeer, Pay-per-view (HBO, Cin- 
emax, Showtime, adult, etc.) $16. 95, $2.00 postage. 
Schematics for Videocypher Plus. $20.00. Sche- 
matics for Videocypher 032, $15.00. Collection of 
software to copy and alter Eprom codes, $25,00. 
CABLETRONICS, Box 30502R, Bethesda, MD 
20824. 



FREE CATALOGS 

1-800-648-7938 

JERROLD HAMLIN OAK ETC 

CABLE TV 



Special Dealer Prices! 

• Compare our Low Retail Prices! 

• Guaranteed Prices & Warranties! 

• Orders Shipped Immediately! 

REPUBLIC CABLE PRODUCTS. INC. 

40B0 Paradise Rd. #15. DeptRE591 ICTT 
Las Vegas, NV 89109 d 

For all other information (702) 362-9026 



V1DEOCIPHER II manuals. Volume 1 — Hardware, 
Volume 2 — Software — either $34.95, Volume 3 
— Projects/Software, Volume 5 — Documentation 
or Volume 6 — Experimentation $44.95 each. Vol- 
u me 4 — Repa i r $99. 95 . Volume 7 — 032/H acking 
S54.95 Cable Hacker's Bible — $34.95. Clone 
Hacker's Bible — $34.95. Calalog — $3.00. CODs 
(602) 782-2316 TELECODE, PO Box 6426-RE, 
Yuma, AZ 85366-6426. 



BUY BONDS 



ELECTRONIC 
ASSEMBLY BUSINESS 



Start home spare time Investment knowledge or 
experience unnecessary. BIG DEMAND assem- 
bling electronic devices. Sales handled by profes- 
sionals. Unusual business opportunity. 

FREE: Complete illustrated literature 

BARTA RE -00 Bui 248 

Walnut Creek. Calif. 94597 



BUSINESS OPPORTUNITIES 

MAKE $50/ hr working evenings or weekends in 
your own electronics business. Send for free facts. 
MJME INDUSTRY, Box 531, Bronx, NY 

10461-0208. 

YOUR own radio station! AM. FM, TV, cable. Li- 
censed/unlicensed. BROADCASTING, Box 130- 
F5, Paradise, CA 95967. 

LET the government finance your small business 
Grants/loans to $500,000. Free recorded message: 
(707) 449-8600. (KS1). 



IMPOSSIBLE 
CABLE SYSTEMS! 



Zenith PZ ♦ Pioneer Cube ♦ Starcom 88 7 ♦ Standard Units 
♦ New Generation of TRII 
♦ Quantity prices start 



■ ^ulji oaf v .:■;,! m.,im. i 

f TRIMODES & SB'S. 

i* $25 each 



Dealers only Call 1-800-933-2242 
SSgital ^Equipment Company ef&nerica 



MAKE $75,000 to $250,000 yearly or more fixing 
IBM color monitors (and most brands). No invest- 
ment. Start doing it from your home. (A telephone 
required.) Information, USA, Canada $1.00 cash. 
US funds. Other countries $8.00 RANDALL DIS- 
PLAY, Box 2168-R, Van Nuys, CA 91404 USA. 



EASY work! Excellent pay! Assemble products at 
home. Call for information (504) 641-8003 Ext. 5192. 

MAKE $SS! Become an American electronics deal- 
er! Profit opportunities since 1965. Call SCOTT 
PRUETT, 1 (800) 872-1373. 



WANTED 

INVENTIONS/ new products/ideas wanted: call 
TLCI lor free information 1 (800) 468-7200 24 hours/ 
day - USA/Canada. 

INVENTORS: We submit ideas to industry. Find out 
what we can do for you. t (800) 288-IDEA. 

NEED help with your electronic project, PCB as- 
sembly/artwork? Write to T.S., PO Box 5275, Flint, 
Ml 48505. 



TUBES - 2000 TYPES 
DISCOUNT PRICES! 

Early, hard-lo-find, and modem tubes. 
Also transformers, capacitors and 
parts for tube equipment. Send $2.00 
for 28 page wholesale catalog. 

ANTIQUE ELECTRONIC SUPPLY 

6621 S. Maple Ave. ■ Tempe, AZ 85283- 602/820-5411 





SUPER 
SALE 

MhM WotM ""v 

73...* 79 M..-MS 

73...M19 w...*229 
77 . . . »149 87 . . . *269 

A. new Model 45 . . . *579 ▼ 
■■£ KEL VIN. Elaarcntos 
5_2 7 Pwrchild Av«„ Plainvim. NY 11803 
aB, (516) 349-7SM 1(600) 645-8218 




DISTINCTIVE RING SWITCH 

Add additional phone numbers to a single line with 

the new Distinctive Ringing service from the phone 

company. RingDi rector detects ring patterns and 

routescallstophones.a nsweri ngmachines, FAX 's 

or modems. 2-port $89. 4-port $149, SIH $5. 

1-800-677-7969 FAX 516-676-9225 

EXCELLENT TECHNOLOGY 

69 smith Street, Glen Head, NY11545 



INVENTORS! Your first step is important. For free 
advice, call ADVANCED PATENT SERVICES, 
Washington, DC, 1 (800) 458-0352. 

TRAVEL! High income! Radio officers wanted for 
shipboard employment. Must have FCC second 
telegraph license. Rae Echols, AMERICAN RADIO 
ASSOCIATION, 5700 Hammonds Ferry, Linthicum, 
MD 21090. 



Be a TV/VCR 
Repair Specialist 

Now you can tram at home in spare time far a money- miking 
career as a TV 'VCR Repair Socialist. No previous experi- 
ence necessary. No need to quit your ;ob or scliool. Everything 
is explained in easy-to -understand language with plenty of draw- 
ings, diagrams and photos. We show you h.ow to troubleshool 
and repair video-cassette recorders and TV sets, how to handle 
npuse cal Is a nd shop repa i r s f or al mo 5 1 any make of television o r 
VCR. Tools are included with your course so you can gel 
"hands-on" practice as you follow your lessons step by step 
Send for free facts about the exciting opportunities in TV VCR 
Repair and find oul how you can start making money in this 
great career MAIL COUPON TODAY «™ 



SCHOOL OFTVAfCR REPAIR, Oepi. ADE0415 
U—uunI 325 Oak Street, Scan ton. PA 18515 
Please send me full informal ion and color brochure an bow I can 
learn TV'VCR Repair at home in my spare time. I understand 
there is no obligation and no salesman will visit me 



Name 

Address 
City/State 



. Ase_ 



_ Apt. #_ 
-Zip 



.Phone | ) | 




racS 



MCM ELECTRON 

6SD CONGRESS PARK DR. 
CENTERVILLE. OH 4545B-4072 
A PREMIER Company 



MCM Electronics 

A Well-Balanced 
Parts Catalog. 

If all you want is a huge assortment of high-quality 
parts and components, we can tip the scales in our 
favor in a flash. After all, we stock more than 16,000 
items, including loads of name brands (3,000 RCA/GE 
parts alone!) and the largest selection of Japanese 
semiconductors in the country! 

But as an MCM customer, you'll enjoy even 
more— like a friendly, well-trained sales staff, 
technical assistance when you need it and a 
GIGANTIC INVENTORY that lets us ship 
more than 98% of all orders within 24 hours! 
So, what are you waiting for? 

Call TOLL-FREE, 1-800-543-4330, 

NOW to get your FREE, 
ONE-YEAR SUBSCRIPTION to the 

MCM Electronics Catalog 



cs 



SOURCE NO. RE-70 



£ 

$ 



87 



CIRCLE 87 ON FREE INFORMATION CARD 



PERFECT CABLE CONNECTION !! 



PeHed Cable Conneclson is totally commiiied 
to cu^omor satisfaction. Our primary concern 
is to provide you with (he highest qu al iiy 
converters and de scram biers al the 'owe si cost 
We employ full lime technicians to insure hassle 
Iree service and iroublesnocl any situation Call 
u* loday and lei us prove to you wtiry we are 
The Parfeci Cable Connection. 



• 6 monlhs 1 00% parts & labor 

■ 24 months warranty available 

• Full lechntcal support 

■ On-line computer system 

■ 30 days money back guarantee 

' Most orders shipped *ilrwn 2* hours 

■ Visa, MC. AMEX ■ 5% 

■ Dealers welcome 

• ao.D 

















JerroW 




Ftogil 


HE 83 W R ' 


Niw" 






400 DAX 3 OtC W R 




1 


S9 ■ ?3 Ch «p*OtV 






1 H9 




10 


S9 ■ Wtrdcas i:m^c 






S 89 




JQ 


65 ■ Automate linfl .Lrfwuj 






10 79 




50 


GO ■ Paronral ock 






20 69 


^■p^^^^^WVp^H 


IOC 


55 ■ Midt m Jwi 






50 6S 






-S 


upwsmH 






ion CALL 






. F 


Mrfa mwnory chmrwk 








J-wrotd 
























1 125 






ZTACS 












HI 


All motels 






Bt^Bml 


20 79 






Cb.1I lor pr*c4K 








50 CALL 














100 CALL 








|j£2 




Jerr^ld 400 






SA-3S 






mvs 


OR* 31 OS W R 




1 


75 




1 


M 






10 


48 




10 


79 


5 « 




to 


43 




20 


65 


10 45 




50 


39 




50 


CALL 


50 40 




100 


35 




100 


CALL 



WE WILL MEET OB BEAT ANY ADVERTISED PRICE 
IN THIS MAGAZINE. 

PERFECT CABLE CONNECTION 

702-358-2763 

2209 Oddie Blvd., Suite 321 
Spark. NV 89431 



THJ£ &Pfl£C tWTOVUTED M A Put*, £ JERVtCS 



A defense 

against cancer 

can be cooked up 

in your kitchen. 



There Is evidence ihaj 
tUei and cancer arc related . 
Follow these modifications in 
your daily diet 10 reduce 
chances of gelling cancer: 
I * Eat more high-fiber foods 
such as fruits and vegetables 
and whole-grain cereals, 
2. include darie green and 
deep yellow fruits and vegeta- 
bles rich in vitamins A and C. 
3- Include cabbage, broccoli, 
brussels sprouts, kohlrabi and 
cauliflower. 

4, Be moderate in consump- 
tion of salt-cured, smoked, and 
nitriu*<urctf foods, 
5 • Cu t down on TOiai fas in- 
take from animal sources and 
fais and oils. 
6. Awrd obesity 
7* Be moderate in consump- 
tion of alcoholic beverages, 

No one faces cancer atone. 



PAMOHCAN CANCER SOCIETY 



CABLE TV. CONVERTERS 

WHY PAY A HIGH MONTHLY FEE? 




All Jerrold, Oak, Hamlin, Zenith, Scientific 
Atlanta. Magnavox and all specialized cable 
equipment available for shipment within 24 
hours. For fast service MC / VISA or C.O.D. 
telephone orders accepted (800) 648-3030 
60 Day Guarantee (Quantity Discounts) 
8 AM. to 5 P.M. C.S.T. CLOSED WEEK- 
ENDS. Send self-addressed Stamped enve- 
lope (60c postage) for Catalog. 



r _,_„ ''_ P.O. 8m 5000 

miDWeST suite mum 



EDUCATION & INSTRUCTION 

F.C.C. Commercial General Radiotelephone li- 
cense. Electronics home sludy. Fast, inexpensive! 
"Free" details. COMMAND, D-176, Box 2824, San 
Francisco, CA 94126. 

BUILD a VCR extender in less than an hour! Play 
TV games in living room, while others watch movies 
in bedroom. Use existing telephone wires to trans- 
mit picture in home; Security, remote control, LAN's, 
and more. Instructions, complete with theory of op- 
eration. $19.95. JZO RESEARCH, Box 28131, Min- 
neapolis, MN 55428. 



CO 

g 
z 

o 

DC 
H 
O 

UJ 

_i 

UJ 

6 
Q 

< 
EC 



88 



COLLIMATOR PEN 
(INFRA-RED) 




LASER DIODE 
(INFRA-BED) 




LASER DIODE 
(VISIBLE-RED) 




LASER DIODE 

(VISIBLE-RED) 




UNICORN - YOUR I.C. SOURCE! 



• Output: 2-5 mW (max.) 

■ Current: 90-150 mA 

• Operating voltage: 2.2-2.5V 

• Wavelength: B20nm 

■ Coltimatron: .ISmrad (lyp.) 

• Size: 11mm diameter 



POWER SUPPLY - Input: 115/230v 



STOCK * 
SB1052 



PRICE 

S39.99 




■ Oulput: 10 mW (max.) 

■ Current: 90-150 mA 

• Operating Voltage: 2.2-2.5V 

• Wavelength: 820nm 

STOCK S PBICE 

SB1053 $9.99 

• Output: 5 mW (max.) 
» Current: 65-100 mA 

• Operating Voltage. 1.75-2.2V 

• Wavelength. 7B0nm* 



LASER DIODE 
(VISIBLE-RED) 




LASER 

POINTER 



STOCK * 

LS022 



PRICE 

$19.99 



■ Output: 4 mW (max.) 

* Current; 20 mA 

■ Operating Voltage: 2.2-3.0V 

• Wavelength: B65nm 

STOCK * PRICE 

LS3200 $99.99 




£ ^UNICORN 

"'^/l LECTRONICS 



Siie 7" L x KM" w x 2U H 

Output: fSvolts£B3.75amp5 
+12 volts @ 1.5 amps 

-12 volts @. 4 amps 



• Output 

• Outpu 
STOCK # 

PS1003 



PRICE 

$19.99 



■ Output: 3 mW 

■ Current: 85-100 mA 

■ Operating Voltage: 2.3-3.0V 
• Wavelength: S70nm 



STOCK • 

LS9200 



PRICE 

$49.99 



< Output: 3.5 mW 

• Wavelength: 670 nm 

* Power Supply 2xAAA 
Batteries (Included) 

+ Beam: Approx 3" 
@ 100 yards 

Quantity Discounts Available 

STOCK * PRICE 

LSPOINT $199.99 







EPROMS 








STOCK* 


1-24 25-99 


100- 


STOCK « 


1-24 2599 


100- 


1702 


4.59 


4 36 


392 


2764A 


3.49 


3.32 


2.99 


1708 


6.49 


6.17 


5.55 


TMS2S64 


5.79 


550 


4.95 


2716 


3.29 


3.13 


2,62 


27C64 


3.29 


3.13 


3.26 


2716-1 


3.79 


3.60 


324 


27128-20 


4.99 


4.74 


4 27 


TMS2716 


5.79 


5.50 


495 


27128 


4.79 


4.55 


4.09 


27C16 


3.99 


3.79 


3.41 


271 28A 


4 79 


4.55 


4.09 


2702 


4.19 


3.90 


3,55 


27C12S 


4.79 


4.55 


4.09 


2732A-2 


37S 


360 


3.24 


27256-20 


5.29 


5.03 


453 


2732A 


389 


3.51 


3.16 


27256 


4.79 


455 


409 


2732A-4 


118 


3.03 


2.73 


27C2S6 


4.29 


403 


3.67 


TMS2532 


5.79 


5.60 


4.95 


27512-20 


6.49 


6.17 


5.55 


TMS2532P 


199 


1.69 


1.70 


27S12 


5.99 


5.69 


5.12 


27C32 


3.79 


360 


324 


27C512 


5.99 


5.59 


5.12 


2764-2(1 


4.29 


4.03 


3.67 


27C1024 


12.99 


1234 


11 11 


2764 


399 


3.79 


3.41 


66764 


13.99 


13.29 


11.96 


2764A-20 


3.99 


3.79 


3.41 


66766 


1299 


12.34 


11.11 




_ DYNAMIC RAMS . 












STOCK i 


124 25-99 


100f 


STOCK* 


1-24 25-99 


130- 


MK4027 


59 


.56 


50 


4464-100 


299 


2.84 


256 


4116-120 


1.39 


1.32 


1 19 


4464-120 


2.79 


265 


2.39 


4116-160 


.99 


94 


.85 


4464-150 


229 


2.13 


1.96 


4116-200 


69 


as 


.77 


41266-60 


2.99 


2.64 


2.56 


4116-250 


59 


56 


50 


41256-60 


2.79 


2.65 


239 


4 161 -100 


1.89 


ISO 


1.63 


41256-100 


1 99 


1.89 


1.70 


4164-120 


169 


1.61 


1.55 


41255-120 


1.69 


1.60 


1.63 


4164-150 


1.59 


1.51 


1.36 


J 1255-1 50 


1,79 


1.70 


1.53 


4164-200 


139 


132 


119 


511000-70 


319 


6.17 


555 


4416-120 


1.99 


1£9 


170 


511000-60 


5.99 


5.69 


5.12 


4416-160 


1.79 


1.70 


163 


511000-100 


5.43 


5.22 


4.70 



10010 Canoga Ave.. Unit B-S * Chatsworlh, CA 91311 
OUTSIDE CALIFORNIA: (BOO) 824-3432 (Orders Only) 

IN CALIFORNIA: (818) 341-8833 

ORDER BY FAX: (818) 998-7975 

Minimum Order 515.00 ■ 24-hour ordering available 



CIRCLE 191 ON FREE INFORMATION CARD 



BLE TV EQUIPMENT 



Converters, Remote Controls, 
Ete scramblers, CD Players. 




tROLD-OAK-SCIENTIHC ATLANTA-HAML1N 
ZENITH MANY MORE CALL TODAY! 

V Only quality products sold V Easy to use 

Satisfaction guaranteed V Knowledgeable sales staff 

V Most orders shipped within 24 hours 
ALL FOR YOUR FREE Q AT A^ Qg 

1-800-228-7404 

MAKE THE CONNECTION 
WITH 



e.1% ELECTRONICS I 



5114Balcones Wood DrJ307 Dept, 298 
Austin. TX. 78759 



MAGIC! Four illustrated lessons plus inside infor- 
mation shows you how. We provide almost 50 tricks 
including equipment tor four professional effects. 
You get a binder to keep the materials in, and a one- 
year membership in the International Performing 
Magicians with a plastic membership card that has 
your name gold-embossed. You get a one-year sub- 
scription to our quarterly newsletter "ITs MAGIC!" 
Order now! $29.95 for each course + S3. 50 postage 
and handling. [New York residents add applicable 
state and local sales tax). THE MAGIC COURSE, 
500-B BiCounly Boulevard. Farmingdale. NY 
11735. 



LEARN IBM PC assembly language. B0 pro- 
grams. Disk S5.00. Book S18.00 ZIPFAST, Box 
12238, Lexington, KY 405S1-2238. 



ZENITH & TOCOM SPECIALS 

SUPER Zenith (2-TAC) converters (flashing) ... 
$179.00. Zenith "turn-on" module... $49.00. 
Tocom 55 03(A) converters... $159.00. Tocom 
(add-on) descrambfers... $79.00. Tocom (5503-VIP 
& 5507) ''turn-on" chips... $49 .00. Tocom 5507 se- 
curity screw removal bits.. .$22,00 CINEPLEX VID- 
EO GROUP. 1 (800) 726-4627. 



PRO 400 



95 



69 



AC'DC VOLTAGE 

AG DC CURRENT 

DIODE TEST Shock No. « 

LOGIC TEST 990092 S 

LED TEST GOOD/SAD 

5 FHE=Q RANGES 

5 CAPACITANCE RANGES 

LOW BATTERY Warning 

CONTlNUfTY TEST/BUZZER 

TRANSISTOR CHECKER 

20 mhzFREQ COUNTER 
5S2 KFI VI M Electronics 



MQNEtBACK 
GUARANTEE* 



VISA 
AfC 



.7 Fairchild Ave.. Plainview. NY 11803 

'(516)349-7610 1(800)645-9212 

FAX (516) 349-7830 




INVENTORS 



INVENTORS! Can you patent and profil from your 
idea? Call AMEHICAN INVENTORS CORPORA- 
TION for free information. Over a decade of service 
1 (800) 338-5656. In Canada call (413) 568-3753. 



MASTERCARD AND VESA are now accepted 
for payment of your advertising. Simply 

complete the form on the first page of the 
Market Center and we will bill. 




THE ELECTRONIC GOLDMINE 



Tto EtartiKifc BAH. 
Has tre rj fie fj&EtiB-. 

IffiHns l* trtoj* tfttktxiit 

We haw Mf 130 
tit; aid (w 1,400 
unique, bargain 
priced, mmpCKiorfc 

-in oj cac&g! 

Inexpensive 
GQGER COUNTER KIT 

Protffjty Ere tows priced Gciger tantr H MitaU in trie 
wdd txfy! Fsalufcs ursine trm va'td Ci'gsr Mueller 
lute and DissKaBdrk: spoer fa mHa dido in praporian 
to She vUob iml Dttsds Bett art Gnma rjyj tfti 
dead ndlurn da ; s on cB voldies, ciacia, ua^gTOLnd 
ratfoiionL. nuettarimu, «c Omy 3: x i & Ocerssifom 
one 9t ttfery (ict ndudrt) Ccmplcie i* all parts, PC 
surd and instructions. 

C6447 $39.95 




■I KV TRIGGER COO. 

UK win any sirctt 

lute i ha n« ce I \ ^ 

3 bad 4tW trigger. ^^ 

NL7O0 $1.25 EA 
100 Jor £-90,00 



^ 



INVERTER 



d 



aTil 4 fcad Irarefomier 
lor use (fit 555 C IP xi Mil 
12VOCioZriVteswte< 
fluHseert UK *rh MJeniale 
N1703 SiOO EA. 
1.000 far $1.500 



PLASTIC 

OFFER CLOSE 

BAGS 

M* now oner high oia.'<r ZM.-' *"<* rtpoerckrse 

tags wiih wtiiLt Was ig wie oa These re- 

coscaoe caps mLrt i zipper locking top lor 

convenient storage d[ sma ' eledipnic vans. 

nanwrt. et m hM nt fclWng sets. 

SoU hi rruticies d 100 cnty. 

2"X 3" G6S3 1O0/S3.30 

3" X t" G6M I00/S3.7S 

3'X 5" G«65 100/S4.O0 

«" X 6" G666 IOOj'SS.SO 



RARE EARTH 
SUPER MAGNET 2 

Many lures srenger man oiher 
magnets. Ixsl it 111 HrtTS 
slranosl oonvnerdiiiy m tapie 

TJC/tS la Sis in Sri Mtor.y 
*W1'iMriW*)»anU12B1Sei Try 
t rtfTwi mis Teqnct Ira-, i see pa: and y:j ■ 
'ind tte unless yw si:* tyoi:c3ntgs Jeff Great 
Icr Ihcyiands of BKpenmtnts and appikatons 
Nwiraitf these st:i i x SCO as\ tui sest at 
augka and raw a Iw icrachca jdoes not died 
Drtwum). Qggg e. 11-00 



MWERAUGHT 
BLACKLIGtfl LAMP 



3" 

raj*i»IW Maotl UVtM la- 
lhbi hilly pafibt operaon Iror. 
four M patleie (KM irclLdMI 
Tnis llpW e ruoged and -js Ire 
lamjssttnnouswnatruaisi 
riDurescent minerals CD glDW 
aijWI). GS12 $29.95 



MINIMUM ODDER: S'0 00 (jkts S3 CO sOccmj ma Iwi 

v/tf icccp* MC. Vea and Vcvy Outers 

SEND ORDERS TO: THil Ek.-arcrtc GOIdmne 

PO Bo« 5403 Scollal* AZ 852B1 

PHONE ORDERS (5021 451-7454 FAX ORDERS 16021 4519495 



CIRCLE 183 ON FREE INFORMATION CARD 



/express 

mM_ 5 in'cfnit'Qpil Inc. 



2-1/2" SANYO TWEETER 

Paper cone with gold tone 
dust cap. S oz. magnet. 
8 ohm. 1/2" ferro lluid 
voice coil. Power 
handling: SOW RMS, 
70W max. Frequency re- 
sponse: 3K-20KH2. 



v-/- 



#RD-271-020 



$1 !i $1 7i 95c 

ji-vj rio-ss] iWupj I 



SUPER HORN TWEETER 



Original piezo tweeter 
made by Motorola. 
SPL=94dB2.83W1M. 
Response: 4KHz- 
27KHz. Handles ap- 
proximately 50 watts. 

#RD-270-010 






$5» $4" $3" 

n -si iw-mi w-urt 



2" DOME MIDRANGE 



Textile dome 
midrange made by 
Philips. 8 ohm. 
SPL-90dB1W/1M. 
30W RMS. 40W 
max. Response: 
550-SKKz. 

#RD-280-210 




15" SUBWOOFER 




10" POLY WOOFER 



Medium 
duty. SOW 
RMS, SOW 
max. 14oi. 
magnet. 
Response: 
25-2.5KHZ. 
fs.28Hz 



I #RD-290-096 




12" CAST FRAME 
WOOFER ^^ 



i 



$18 M $16* 



Dual voice coil. 40 oz. magnet. 6 ohm 
imp. 10OW RMS. 140Wmax. Response: 

20-1.2KHZ. Resonant frequency: 21 Hz. 
SPL=93dB 1W/1M. 



#RD-290-190 



S54 5 ' 



$49" 



SUBWOOFER XOVER 





200W RMS crossover designed 
specilically for use with dual voice coil sub 
woofers. 12 dB per octave roll-off at 



#RD-260-220 



$28" $24* 



340 E. Fi.il St.. Daylm, Ohio 45+02 
Local: 1-51 3-222-01 73 
FAX: 51 3-222- 4644 



• IS day mafiey back guarantaa - Si 5.00 niinimjm ordar * wa accept 
Masigreard, Visa. Discover, and C.O.O. oroars. - 24 hour shipping - 
Snipping charge - UPS ctian. raia + SI ,00(sa.00 minirmjnn charge) ■ 
Hours o^Q am. 7:00 pvn EST. Monday ■ Fnday - Mail order custom- 
ers, please call lor shipping estimate on orders exceeding 5 lbs. 
Foreign customers please send 55.00 U.S. runds lor catalog postage. 



TITANIUM COMPOSITE 
TWEETER 

The advaniages of 
both hard and soft 
dome technologies. 
8 ohm. Ferro fluid 
cooled voice coiE. 
SPL=90dB 1W/1M 
SOW RMS. 70W 
max. 4" round. 
PolydaK 
#DTW100T125, 



#RD-270-047 

SPEAKER BUILDING 
BOOK 

Revised edition 
of David Weems' 
best selling book 
Learn to build low 
cost speakers 
that rival the high 
priced models 

#RD-50r>021 

CALL TOLL FREE 
1-800-338-0531 



i 

v 



C^*. 



12" woofer made in the USA by Eminence. 
Paper cone and dust cap with treated cloth 
surround. 80 oz, magrret. 2-1/2" vented 
voice coil 8 ohm 170W RMS, 235W max. 
40-4.5KHZ response. 



#RD-290-147 





CIRCLE 56 ON FREE INFORMATION CARD 



5 



89 



o 
z 

o 

d 

LU 



Q 

D 
< 

DC 



SCIENTIFIC & ELECTRONIC 
PRODUCTS 



LASERS AND SCIENTIFIC DEVICES 

VRL2K 3mwV!s Red Laser Diode System Kil $159.50 

LUSIK Lsstr Beam "Sou nc«" Listener Kit S199.5FJ 

LHC2X Visible Simulated 3 Color Laser KI1 $14.50 

LC7 40 Wall Burning Colling Laser Plain SZG.OD 

RUB4 Hi Powered Poised Drilling Laser Plans ;.„... ..,.$£0.00 

LGU4D 1 to : ■ 1 1 1 . .■ HeNe Vis Red Laser Gun Assembled S1S9.00 

LLS1 Laser Lite Shnw- 3 Methnds Pljns S20.00 

SD5K See in Ibe Dark Kit SZ99 ,80 

EML1K Eleclromarjnelic Coil Gun Kit $69.50 

MCP1 Hi Velocity Coil Gun Plans S15.00 

LEVI Ltvtlilfnrj Deyite Plans S10.DD 

EM1 Electronic Hypnotism Techniques Plans ; ,,..,..510.00 

HIGH VOLTAGE AND PLASMA DISPLAY DEVICES 

HVM7K 75.000 Veil DC Variable 0ui|)ut Lab Source Kit 5149.50 

ICIGoK Ion Roy Gun Kil. project energy withnul wires $69.50 

NIG9K I2V/115 VAC Hi Ool Neg Ion Generator Kit 534 51- 

EMA1K Telesinetic Enhaocer/Electric Man Assembled $99.50 

1G5K Lightning Display Globe Xil 554.50 

BTC1K Worlds Smallest Tesla Coil Kit $49.50 

8TC3K 250KV Table Top Tesla Coil Kit ....$249.50 

BTC5 1.5 Million Volts Tesla CdII Plans $£0.OD 

Ji. 3 Jacobs Ladder -3 Models Plans $15.00 

GRA1 Anti Gravily Generator Plans $1 0.00 

PFS20 Plasma Fire Saber Assembled $09.50 

D PL. :'■ Dancing P I as m a lo Music a nd Sou nils Assembled $79.50 

SECURITY AND PROTECTION DEVICES 

ITM10 100,900 Voll Inlimidalor up lo 20' Assembled $129.50 

IPG70 Invisible Pain Field Blast Wave Gen Assembled $74 50 

PSP4K Pbasor Sonic Blast Wave Pistol Kit $59.50 

LISTI0 Inlinlly Xmtr. Listen in Via Phone Assembled $199.50 

TAT3D Automatic Tel Recording Device Assembled $24.50 

VWPH7K 3 Mi. FM Auto Tel Transmiller Kit $49.50 

FMK1K 3 Mi FM Voice Transmiller Kit $39.50 

HD01K Homing/Tracking Beeper Transmitter Kit, $49.50 

EASY OFtDCBING PROCEDURE TOLL FREE 1.SCD-22M 7D5 

or 24 HUE OH 1 -603- 573 -4730 or FAX IT TO 1-E03-572-540S 

VISA. MC, CHECK. MO III US FUNDS INCLUDE 10-.i SHIPPING DROEflS 

S100.UO4 UP ONLY ADD S10.00. CATALOG 51.00 OR FREE WITH OP DEO. 



INFORMATION UNLIMITED 

P.O. BOX 716, DEPT. R3, AMHERST, NH 03031 



CABLE TV 
DESCRAMBLERS 



Qty 


1 10 20 


Jerrold (Type) SB-3 


89.00 56.00 43.00 


Jerrold (Type) FTB-3 


99.00 69.00 54.00 


Scientific Atlanta SA-3 


99.00 69.00 54.00 


Hamlin MLD-1200 


99.00 50.00 45.00 


OakN-12 


99.00 59.00 58.00 


Tocom 5501 


169.00 139.00 125.00 


Eagle PD-3 


119.00 64.00 60.00 


COMBINATION UNITS 


Jerrold (Type) DRX-3DIC 


169,00 109.00 89.00 


Jerrold (Type) Starcom 6 


279.00 239.00 209.00 


Scientific Atlanta 8535 


229.00 209.00 199,00 


Scientific Atlanta 8580 


299.00 269.00 259.00 


Oak M35B 


99.00 59.00 49.00 



OTHER TYPES ARE OFTEN AVAILABLE 



* We specialize in 

large quantity discount 

* Call us for pricing 

on 50 and 100 lot 

* We will not be undersold 

on large quantities 

* Please have the make and model 

number of the model you need when 

calling for information 

K.D. VIDEO 

P.O. Box 29538, Mpls. MN 55429 
TOLL FREE 1-800-327-3407 



NEXT MONTH IN Po pular Electronics 



Exciting Features, Projects, Reports, & Columns 

• A NEW DECADE IN • BUILD THE PROTOMAX 

CONSUMER ELECTRONICS PROTOTYPING STATION 

Circuit design is a snap when every- 
thing is at your fingertips 



There's plenty of high-tech excite- 
ment in store for the 1990s 

• EXPERIMENTS IN 
ELECTROCHEMISTRY 

Fascinate yourself and your friends 
with these fun experiments 



• BUILD THE 
ACCESS III 

A telephone-operated, remote-con- 
trol power switch for your computer 



Po pular Electronics 




And there is more! 



PRODUCT REVIEWS— Sony Au- 

dio/Video Switcher, Nakamichi CD 
Player2 CD Changer, Memorex 
Headphones, and more 

DX LISTENING— Tune in to Radio 
Bangladesh 

COMPUTER BITS— What good is 
Hypertext? 



1INK TANK — A primer on cur- 
rent-limiting resistors, a telephone in- 
tercom system, a Christmas-tree 
light tester, and more 

HAM RADIO — Some simple fixes 
for annoying problems 

ANTIQUE RADIO— America's love 
affair with the Theremin 



PICK UP lu piUdi IlCUlUlllta AT YOUR FAVORITE 
NEWSSTAND, CONVENIENCE STORE, OR SUPERMARKET. 



90 



* * * * PRESENTING * * * * 

CABLE TV 
DESCRAMBLERS 

***** STARRING ***** 

JERROLD, HAMLIN, OAK 

AND OTHER FAMOUS MANUFACTURERS 
- FINEST WARRANTY PROGRAM AVAILABLE 

• LOWEST RETAIL (WHOLESALE PRICES IN US 

• ORDERS SHIPPED FROM STOCK WITHIN 24 HRS 

• ALL MAJOR CREDIT CARDS ACCEPTED 
FOR FRIE CATAIOG ONLY I-80O-345-8927 

. FOB ALL INFORMATION 1-018-709-993^/ 



PACIFIC CABLE CO.. INC. 

7325 r /j Reseda Blvd.. Dept.2102 

Reseda. CA 91335 



PAT TV AND SATELLITE DE SCRAMBLING 
ALL NEW 1991 EDITION 



Olk nasi yet Tfte very laEcsl in desyimWing preurts , fr/pasas, lurn-em for 
cable, wireless and satellite Only SU.M Oihe r -av T^' editions, '-'-z T (Ba&cs 
of AB Systems) SI 4.95 1 939 f (Sffiw SI 4 35 Bwld saldm* Systems under $600 
SI 2.95. Wireless Cable ttar.dbgrtS9.95 Any i<S24 95 at S^4 K. Scrambling 
News Momhfy has all inlo on ihg abw "Plain Vanilla" descrarnblers which Em- 
ulate B-Mac.VCII. Plus anfl Orion S19 95=yi All -.erv-' c*in.og Jl 



Scrambling News, .552 Hertel Aug., 
Bulfalc. NY, 14216. COD'S ARE DK. |716| 8/4 2088 



THIS IS AN EXPANDED TYPE AD. Notice 
how it stands out on this page. To getyour ad 
set in this type style mark your classified ad 
order, "Expanded-type ad," and calculate 
your cost at $4.70 per word. 

THIS IS AN ALL BOLDFACE AD. If you want your 
entire ad in boldface the cost is S3.65 per word. 



■WIS SPACE GOWmHLnFD A5 A U C SFftv^E 



When someone 

in your family 

gets cancer, 

everyone 

hi your family 

needs help. 



Nobody knows bctier than 
we do haw much help ami 
urLdertT.ariEliTig Ls needed, Thac's 
why our service and rehabilitation 
programs emphasize the whole 
family, mil just the cancer paiiem. 

Arrmiig owr regular services 
wc provide infornriaiirjn arirdi 
guidance \o patients and famihes. 
transport paitcnis to and from 
rreaiment, .supply home care items 
and assist patients in their return 
to everyday life 

J.ilc is what concerns us. 

So you can see wc arc even 
mure t han the research organi- 
zation we ate so well' known to be. 

No one faces cancer atone. 



fAMUiiaW GWCES! SOCIETY 



WARNING! 

CABLE BOX DEALERS 

Consider the facts before you buy 

after-market cable equipment 

An industry standard defines 25% of all 
after-market cable boxes do not work when 
first tested... 

All wholesalers advertise low prices. ..but 
low prices are not enough. Any price is too 
high if you're without technical support or 
quality control. 

Now consider that your success as a 
dealer depends on the satisfaction of your 
customers. 

Wholesale Cable Supply offers services 
that are near a defined science. And we 
guarantee 100% satisfaction. 
Monthly special • Guaranteed Low Prices 

• State-of-the-Art technical support 

• Top Quality Tested Products 

• Dealer Market Support 
WHOLESALE CABLE SUPPLY 

Low Price is only the beginning 
1-800-962-6836 
723 CAMINO PLAZA, STE. 108, SAN BRUNO, CA 94066 



TB-3 or 


SA-3B 


10 lot 48 


20 lot 


- 43 


50 lot 


-39 


100 lot 


-39 


Z-TAC 


10 lot - 


149 



MARK V €L€CTRONICS, INC. 

Competitive Pricing * Fast Shipping Since 1985 



A indicates the level of difficulty in the assembling of our Products. 




Amplifier 

+ 
Metal Cabinet 

+■ 
Transformer 



Kit Set 
Assmb. Set 



TA-3600 

LG-192S 

#007 



$155.61 
$179.36 



TA-477 

LG-1925 

#003 



$125.21 

$141.36 



TA-8Q2 

LG-1924 

#001 



$100.45 
$113.54 



TA-1000A 

LG-1924 

#001 



$113.52 
$133.36 



TA-1500 

LG-1925 

#001 



ORDER IN CALIFORNIA 800-521-MARK 
ORDER OUTSIDE CA 8Q0-423-FIVE 
FREE CATALOG & INFORMATION (213)888-8988 
FAX (213) 886-6868 



A Beginner iA Intermediate AAA Advanced * Fully Assembled 

TA-1000A 



$130.00 

$150.00 






TA-302 



1 Due lo this special otter & low price, wc can only exchange or repair any of ihose units (TA-3600. TA-477. TA-802 

5 TA-1OO0.A) wilhin lStfayS □! your receipt 
1 Th* above prices are lor the complete sets. For separate unit price, ptease see beJow Transformer 



, IB 




TA-477 -'/ 
Metal Cabinet 





AMPLIFIERS 



KIT ASSEMB 



MISCELLANEOUS 



KIT ASSEMB. 



MODEL 

TA.2BMK2 

TA-50A I E 

1A.50C 

TA-120MK2 

TA-300 

SM 302 

TA.323A 

FA-377A 

TA-400 

FA-477 

IA-30OMW 

TA-302 

TA-IO0OA 

r*-i500 

TAKOO 

IA?iC«S 

TA-3SO0 

TA-26O0 

TA-30O0 

TA-3600 

SM222 

SM328 

SM333 

SM-666 

SM-gw 



DESCRIPTION 

Dtgilai Voice Memo AA 

Mullr-Pwrpose Melody Generator A 

Multi-Perpose Melody (Happy BilMay. Wedding March, etc ) 

35W Pass 'A' Main Power Mono Amp AA . 

30W Mulli-Purpose Single Channel Amp, A . 

SOW . SOW Stereo Power Amplifier (wrtti vOc ineutiAA 

30WX 2 Stereo Pre- main Amp A 



Stale or Ihe Art FuUy Complementary Symmetrical FET Pre- 

40W Solid Slate Mono Amp A 

120WM0Slel Power Mono Amp AA , 

I20W < i mw i on Tim Pre-Main Sleieo Power Amp. a a 

SOW i SOW Pure DC Stereo Main Power Amp AA 

tOOw Dynamic Class "A" Man Power Mono Amp a a . 

10OWX2Class"A" DC Stereo Pre-Miin Amp AAA 

DC Fel Super Pass "A' DC Pre-Amp AAA 

i scire nic Echo S. Reverberation Amp * 

HO Pre-Amp wnG band graphic equalizer + 

Bt-FET IC Pre-Amp w/3 way lone control A A 

SEereo Simulator | For Mono TV or Any Mono Source) A A 

30DW HO Hi-Fi Power Mono Amp AAA 

i Banc HI Fl Graphic Equalizer a a a 

4 Channel Prolessional Color Lighl Controller* 
AudscWideo Surround Sound Processor AAA* 
Dynamic Naise Peduolron A 
Oniiersal Aud.OTldeo KARAOKE Ml)«. Pre-Amo 




«90 

..Z7 0O 

SS 00 

Z6 30 



65 00 
2S.0O 



1720 
18.71 
'2.S0 
23 00 

7BO0 
42 80 
7S00 
34.93 

65.00 

53.72 

'80 58 
SS.I1 

ua 

36.00 
68 30 
63 57 
3830 

11000 
38 80 

145 00 
75.00 
34.00 

225 00 



MODEL 

TV-23B 

1Y-25 

TV-35 

TY-36 

TY-36 

TV-ilMKV 

TY^2 

TV-J3 

TT-45 

TY-47 

■0 OOOj ' 



DESCRIPTION 

3 Channel Color Light Controller * 

Stereo Loudspeaker Protector A 

FM Wireless Microphone A 

al roc Quart? Digital Clock a 

Sound /Touch Conlrol Swnch A 



inwred nemoie Control IMii rw.'Case) aa a 
Bar / Dot Level Meter AA 

3vs Diniiai panel Meter a 

20 Steps Bar I Dot Audio level Display A A . .. 
Superior Electronic Roulette A A 



80 V Capacitor (Snpgesled for TA-3600 TA-477, TA-1000A S TA-602) . 



..S 

14.85 

11.25 

19.00 

1100 

22.00 
...34.1S 
. . 29.00 

33.45 

. 13.46 



S6SO0 
20.B5 

26.20 

35.00 
33.61 
38.00 
46.14 
27.24 
23 00 



REGULATORS 



XJT 



m-35SA 0-1SV5AReoul)ledDCPovierSuppt((noca5eSiformer|A 515 65 5 21.76 

TH-355B 0-30V SAReoutaled DC Power Supply (no case iKtormecl A _ 15 65 21.76 

TR'603 0-SOV3AReguUied DC Power Supply (no case iitormeri A a ... .10.75 23 55 



METAL CA8IWETS WITH ALUMINUM PANEL 



MODEL 
LG-1273 
LG-1664 
LG-1924 

LG-1325 
LG-1983 



H'lW K D' 

3-12-7- 
4 k IF 

4- ir 

5' 19' 
.'■, 19' 



UATCHINS 

1A-3300,TA-377A,-tA-2200 
TA-323A. TA-377A TA-2200 



r 

It", TA-g02.TA-15O0,TA120M1i2 TA-300MK2. TA-100DA 

It 11 TA-477. TA-600. MK2 TA-1SO0. FA-1000A TA-36O0 .. 

8" TA-377A. TA-2B0O TA-2200 TA-120MK 2 



PRICE 
322 85 

. .27.50 
00 60 
.35.30 
79.25 



POWER TRANSFORMERS 



DIGITAL METERS AND COUNTER 



KIT ASSEMB. 



SM-43 3: .- MullJ-Functic real Led D P M lvr>ABSplasliccase)AA 

SM-46 1 ' .- Hi -free so r. G P M A A A 

SM48A 4'-,. Hi. Precision D.P M iw'ABSclaslic caseOAAA 

SM-43 3^ Mulh-Funchoral LCD D M p (vvllo'd Func1ion|AA 

SM10O 1 SOMC DigrlaL f reguency Counter A A A 

^C-IOOOA 1 GHz Frequency Counler * . 



. 334 50 343 00 

38.00- 43.00 

41 20 52 00 

3600 44 50 

79 00 90 00 

17300 



MODEL 

001 

00? 

003 

004 

0O5 

006 



DESCRIPTION 

23V I 2 CA 10 30V 1 2 6A 

36V i 2 3A 

40VI26A 

24VJ2 6A 

26V X 2 3A 



MATCHING PRICE 

TA-800 MK2. TA-802. TA-8J0A. TA-I000A. TA-1500 . S 27.00 
TB-503. TA-323A TA-400, TA-300. TA-377A . ... 22 00 

FA-177 .28.00 

TA-120MK2 „_ 22.00 

TR-355B 16.00 

TR-355A IS 50 



5 



.'.■ ,..■:- i .'■■■;- ..-,■..!■ man , ■■■ -i. ■ ChKftta IC.OI3 kshn EiOJJ.lwtata '.' i ■■■■■!■ ■ j. -.■..■ ;■:.,..'-;:■ •: •>,. n-, . -.1 ;,:..;■■ , Gu'Mi !•>':■:. ?. Sho-.vroorii Iioj"'. iP.;iuin: rbne 

outKMUS 1*aaA*c&outiatooacMfr>ir*'tarQrf5mri r nviF2*i* <*tott<&\ariten . * aii ika^nifi!^ uno 'tiiw 1 30 di^ w *Ans4tns Mon Ihtu Fn. 9:30 am lo 5:00 prh 

at ca pwrno «dd m**» lu 9 .75"*. ' Ail mrchar> Qr» tf -etfu ire sutfrea topic* «Je Prce* -vo sijduici tocna^*it»^ip» 1 c'«^cw W#w*rw Sat. HO 00 am lo 5.00 pm 

MARK V ELECTRONICS, INC. - 8019 E. Slauson Ave, Montebello, CA 90640 ^H^] 



CIRCLE 93 ON FREE INFORMATION CARD 



UJ 
I 

O 

Q 
< 



Eli 



'Radio 



REPRINT 
BOOKSTORE 



□ 221 Popular Electronics (1991 back Issues) $4.00 

Write in issues desired 

D 220 Popular Electronics (1990 back issues) $4.50 
Write in issues desired 

□ 119 Popular Electronics (1989 back issues) $4.75 

Write in issues desired 

□ 118 Hands-On Electronics (1988 back issues) 

$5.0(1 

Write in issues desired 

□ 117 Hands-On Electronics 

(1987 back issues) $5.25 

Write in issues desired 

O 116 Hands-On Electronics 

(1986 back issues) $5.50 

Write in issues desired 

□ EH91 Experimenters Handbook (1991) . . . .$4.50 

□ EH90 Experimenters Handbook (1990).,.. $5.00 

□ EH88 Experimenters Handbook (1988-89) $5.50 

□ EH87 Experimenters Handbook (1987) . . . $6.00 
D HH91 Popular Electronics Hobbyist Handbook 

(1991) $5.00 

□ HH90 Popular Electronics Hobbyist Handbook 

(1990) $5.50 

□ HH89 Popular Electronics Hobbyist Handbook 

(1939) $6.00 

D 126 Radio-Electronics Annual 1986 $6.00 

□ 211 Radio-Electronics (1991 back issues) $4.00 

Write in issues desired 

P 210 Radio-Electronics (1990 back issues) W.5Q 

Write in issues desired 

D 109 Radio-Electronics (1989 back issues) .$4.75 

Write in issues desired 

D 108 Radio-Electronics (1988 back issues) .$5.00 

Write in issues desired 



□ 107 Radio-Electronics (1987 back issues) $5.25 
Write in issues desired 

n IBS Radio-Electronics (1986 back issues) $5.50 
Write in issues desired 



REPRINTS REPRINTS 

I I 169 TiiinkTank (133 Circuits) $3.50 

□ 169A Think Tank Vol. 2 S3.BD 

□ 168 Fact Cards (#34-66) S4J0 

□ 168C Fact Cards (#67-99) $3.50 

a 168D Fact Cards (#100-132) $3.50 

D 167 Designing With IC's $4.00 

["J 166 Collected Works ot Mohammed Ullyses Fips 
(62 pages, April Fools Collection) .... $5. DO 

□ 165 How to Repair CD Disc Players $5.00 

□ 164 Modern Electrics [April 1908) $3.00 

□ 163 Receiving Satellite TV $5.00 

D 162 Build Your Own Satellite TV Receiver $5.00 

D 161 Descrambling (Feb. 1984) $3.00 

CI 160 New Ideas - 42 Circuits $3.50 

n 159 Low Frequency Receiving Techniques 

Building and using VLF Antennas S5.00 

□ 15B Electro Importing Co. Catalog 

(Circa 1918) $5.95 

□ 157 All About Kits $2.00 

□ 156 How To Make PC Boards $2.00 

□ 155 IBM Typewriter To Computer $2,00 

□ 154 How To Repair VCR's S3.S0 

□ 150 Pay TV Decoder (1981) $3.00 



To order any of the items indicated above, check off the 
ones you want. Complete the order form below, include 
your payment, check or money order (DO NOT SEND 
CASH), and mail to Rarlio-Eleclrortics, Reprint Depart- 
ment, PC. Box 4079. Farmingdale, NY 11735. Please 
allow 4-6 weeks for delivery. 



If you need a copy of an article that Is In an issue we 
indicate is unavailable you can order it directly from us. 
We charge 50$ per page. Indicate the Issue (month & 
year), pages and article desired. Include payment in 
lull, plus shipping and handling charge, Make checks 
payable to Gernsback Publications. Inc. 



ARTICLE 



PAGES 



MONTH 



YEAR 



TOTAL PAGES 



(a 50 C each 



TOTAL PRICE 



MAIL TO: Radio-Electronics 

Reprint Bookstore. PO. Box 4079, Farmingdale NY 1 1735 

SHIPPING CHARGES IN USA & CANADA 

50.01 to $5.00.. $1.25 $30.01 to 40.00 ... 

$5.01 to $10.00 $2.00 $40.01 to 50.00 . , . 

$10.01 to 20. 00 S3.00 S50.01 and above.. 

$20.01 10 30.00 S4.00 



S500 
S6.00 
S7.50 



All payments must be in U.S. lends 

SORRY - We only ship to USA 8 
Canada 



Total price of merchandise $ . 

Sales Tax (New York Slate Residents only) $ . 

Shipping Charge (see chart) $ . 



Name 

Address . 



Total Enclosed. 



City. 



.State . 



.Zip. 



RE591 



PCN 



continued from page 74 



for the most part favoring the set- 
aside of spectrum for PCN's 
(providing it comes from some- 
one else's allocation). It will take 
at least three to four years (and 
that's optimistic) until the dust 
settles and permanent alloca- 
tions to PCN's are made. If the 
tests show that spread spectrum 
is indeed a feasible way of intro- 
ducing PCN's without treading 
on the toes of the current spec- 
trum users, the FCC's problem 
will be largely solved. Otherwise, 
it will have to clear spread spec- 
trum by ordering occupants to 
move to a higher band. After that, 
the FCC then has to consider the 
rather large— and perhaps over- 
whelming — problem of how to li- 
cense PCN's. 

One possibility of licensing 
PCN's is the cellular paradigm. 
The FCC divided the country up 
into over 700 markets, urban 
and rural, and allotted two licen- 
sees to each, one for the tele- 
phone company in the area, and 
one awarded by lottery. While the 
process led to a lot of people get- 
ting extremely rich, especially 
those involved in preparing ap- 
plications for licenses, results 
were less than satisfactory, since 
two cellular companies have not 
provided adequate competition 
(cellular usage prices have not 
fallen since services were inaugu- 
rated in the mid-80's). Another 
possibility is to have two to four 
national licensees or, alter- 
natively, licenses could be 
granted on a regional basis with 
two or three licensees in each re- 
gion. If the FCC chooses that ap- 
proach, there will be a feverish 
scramble for whatever licenses 
are offered and there will cer- 
tainly be several sore losers. 

The upshot of all this is that 
many of Americas largest compa- 
nies will be scurrying frantically 
in the next few years to ensure 
that when the dawn arrives, they 
will have secured their share. The 
ultimate beneficiary will be the 
communications user, who will 
have a new-found freedom to go 
anywhere without sacrificing the 
ability to keep in touch with any- 
body at any time. R-E 



92 



We Have QUALITY PARTS • We Have DISCOUNT PRICES > We SHIP FAST 



m<m®mm<&M 



24 VdC MINIATURE 
GEAR MOTOR 



•n DC motor # 

910 61.112 060 

gwtlh no load: 
Jc@5ma-f6SRPM 
fc @> 5 ma -84 HPM 
slon goat maor. 
)ned for 24 VdC. 
aw on 12-24 Vdc. 30:1 gear reduction 
. 2.07 long X 1.18" square mounting brack- 
6 mounting holes on 0.97" centers. Motor 
lood torque whan used at 24 Vac. 
CAT*MOTG-15 $12.00 each 



I.E.C. POWER CORD 12 Vdc POWER PACK FLOURESCENT FIXTURE 





6 foot BLACK, SPH-386 jack to 3 
prong molded A. C. plug. Fits most 
computers, computer terminals and 
test equipment. 

CAT#LCAC-C6 $3.00 each 




12 Vdc 1 Amp. power pack, 8 ft, 

2 conductor pwoer cord on input. 

22* cord with stripped and tinned pigtail 

leads on output. 3.2" X 2.3" X 1.9". 

CAT#DCTX-121 $5.75 each 




Fixture for single mini bi-pin 6", 4 wall lluores- 
cent lamp. Starter switch, sockets and ballast 
are mounted on 7 1/4" X 3 1 /4" malar plate. 
Includes 8 toot power cord with slrain relief. 
Use with standard fluorescent lamp for display 
Fighting or with ultraviolet lamp lor special at 
leas or EPROM erasure. u.L. listed. 
CAT*FLX-1 $3.00 each 



SWITCHES 



Dtp P.C. Pushbutton 

Schadow Digriasi 

mSE 

D.T. momentary 

iburton. Mounts in 

in DIP conliguration. 

gned for low current switching appli- 

ms. Grey keycap Is 0.68" X 0.67", 
CAT4PB-2S f 1.00 each 
10 lor $9.50 ■ 100 for $85.00 

rcury Tilt Switch 
diameter 

65' long 



=€D 



jury tin switch, S.P.S.T.Croses circuit 
n switch Is tilted approx. 5 degrees. 
CAT#MS-3 $1.00 each 
10 lor $9.50 • 100 for $85.00 

tary BCD Switch f—± 

»# 2310-026 \%1 

) 10 position ^f-W 

try swkch. DIP configuration fits in 
idard 8 pin I.C. socket. Right angle 
3. Screwdriver actuation. 0.42* cube. 
CAT#RDIP-2 }l. 75 each 
10 for $16.00- 100 for $145.00 

Miniature Toggles 

Rated: 3 amps @ 120 Vac 
.D.T. (ON-ON) P.C. mount 
t#MTS4PC $1.00 each / 

or $9.00 - 1 00 for $60.00 J> 

! O. T. (ON-ON) solde r lug s £*. 
'*MTS-4 $1.35 each Cl 

or $12.50 -100 for $110.00 ^r 
'.D.T, (ON-QH) solder lugs 
T#MTS-8$1.75ea. 1 f or $ 1 S.OO 
'.D.T. (ON-ON) P.C. mount 
T#MTS-SPC $2,00 ea, 10 lor $17,50 



LEPHONE KEYPAD 



Sutton telephone 

pad. Ivory finish. 

3" x 2,2" x 0.58- thick. 

Irix encoded. 

al for telephone or 

writy keypad. 

T#KPT-l$1.00each -I0for$9.00 



OPTO-SENSOR 



W/Oplron - OPB5447-2 
rtmilter/sensor pair in , j " T fc 
aang ular package wfth f([ 3?£"B 
color coded leads. 
TiOSR-4 2 for $1.00 



~J 






PH0T0FLASH 
CAPACITOR 



Rubicon CE 

210 Mid 330 Volt 

photoflash 

capacitor. 

0.79" oTa. 

X 1.1" high. These are new 

capacitors that have been 

propped with 1.4" black and 

red wire leads soldered lo Ihe 

terminals. CAT* PPC-210 

$1.25 each -10 for S1 1.00 
100 for $100.00 

Large quantities available. 
Call for pricing. 



RECHARGEABLE 
BATTERIES 



6 Volt 1 Amp/Hour 

Japan Storage B artery Co. 
Portalac w=f»s^? 

#PE6V1 VS-J^ 

6 Volt 1 Ah h Y^ 

rechargeable J 

sealed lead-add v ~~~^^ 
(gel celt 2" X 1 .635" X 2" ht. 
Batteries are propped with 5' 
black and red leads terminat- 
ed wilh 2 pin connector, 
CAT4GC-61 $4.75 each 
10 for $42.50 

Nickel-Cad 



AAA SIZE $1.50 each 

1.2 veils 1 BO mAh 
CAT* NCB-AAA 

AASIZE $2.00 each 

1 .25 volts 500 mAh 

CAT* NCB-AA 

AA SIZE $2.20 each 

WITH SOLDER TABS 

CAT* NCB-SAA 

C SIZE $4.25 each 

1.2 vote 1 200 mAh 

CAT* rMC B-C 

DSIZE $4.50 each 

1 .2 vote 1200 mAh 

CAT* NCB-D 



HALL EFFECT SENSOR i P.C. RELAYS 



Microswrtch *SS41 
Tiny, solid state switch 
reacts Instantly to 
proximity of magnetic field. 
Operates at extremely high speeds, up to 
100 khj. Case siie: 0.12" X 0.17" X0.06" 
thick. 4.5 Vdc to 24 Vdc supply voltage. 
10 ma sink type digital output. Operating 
gauss - 1 5 to 40. P.C. leads. 
CAT* HESW-3 $1.00 each • 10 lor $9.00 
1 00 for $65,00 ■ 1000 for $750.00 



INSTRUMENT ENCLOSURES 



High quality molded 

ASS Instrument 

enclosures. Integrated 

PC board standoffs 

and two eets of 

vertical mounting skits for front and rear 

sub panels. All enclosures are 6" wide X 

6 1/4" deep. Choice of three his. includes 

non-skid rubber leel and hardware. 

Available In beige. Ivory, black, and blue. 

F-an*jftL CAT* 

21/4' CATJTMB-A I7.50«ach lOtateSOO 

2 J*fi* CAT* M B- B 17 75 * adl 1 lor S67 50 

y CAT* M B-C Sfl CO (-m 1 br 170 00 

Plu&a specify color. 



RG-11/U VIDEO CABLE 



100 ft. or 200 ft. rolls 

ol RG 1 t/U 75 ohm 

cable terminated to 

heavy duty F 

connectors. Includes 

75 ohm terminator and ■« * ■■ > i 

F-S1 splicer on one end. 

New cables manufactured for IBM PC 

networks. IBM PIN 1 501908 COMrSCOPE. 

CAT* RG-tt-l 100 ft. roll $15,00 

CAT* RG-1 1-2 200 It. roll $27,50 



FLASH ASSEMBLY 



New compact flash 

assembylroma 
U.S. manufacturer of 
cameras. Operates 
on 3 Vdc and measures GEXOXEJ' 
21/2"x11/4", IdeaJ for use as a slrobe, 
warning light or attention getter. Includes 
hook-up diagram. CAT* FSH-1 $3.75 each 
10 lor $35.00 - 100 lor $325.00 






The following 

relays all have 

p.c. pins lor 

both Input and 

output as well 

as quick-connect terminals 

ontheoutput. 1.5"X 1.05" 

X1.08-, UL&CSA listed. 

IZVdcSPDT 
Potter & Brumfiefd * 
T91R5D22- 12-02 
12 Vdc 155 ohm coil. 
Normally open contacts rat- 
ed 20 amps, Normally closed 

contacts raied 10 amps. 

CAT#RLY-31 $2.50 each 

10 lor $22.50 

12 Vdc, SPST N. O. 
Potter & Brumfleld # 
T91R5D22-12-01 
12 V<Jc. 155 ohm coil. 
S,P.S.T. normally open con- 
tacts rated 30 amps, 
CAT* RLY-32 $2.00 each 
10 lor $13.00 



L.E.D.'S 



Standard JUMBO 

I Diffused T 1 -3/4 size (5 mm) 



BED CAT* LED-1 
10 for $1.50- 100 lor $13.00 

GREEN CATKLED-2 
10 for $2.00 ■ 100 for $17.00 

YELLOW CAT* LED-3 
10 for $2.00 • 100 for $17.00 

FLASHING LED 

W/ built in Hashing circuit 

5 volt operation. T 1 -3/4 

(5mm) ^ 

i. *^»^^ 

RED $1.00 each 
CAT*LED-4 10 for $9.50 

GREEN $1.00 each 
CAT* LED-4G 10 for $9.50 

YELLOW $1.00aach 
CAT*LED-4Y101or$9.50 

LED HOLDER 



L.ED. FLASHER KIT 



&&~\ 




Two L.E.D.'S flash In 
unison when a 9 volt 
battery is attached. 
This kit includes a <s^~~ ' 

p.c. board, all the pans 
and instructions to make a simple Hash- 
er circuit, A quick and easy project lor 
anyone with basic soldering skills. 
C AT* LEDKIT $1.75parkil 
LE.D. CHASER KIT 

BuiW this variable 

speed led chaser. ■ *' JVjj \£i 
10 leds flash ^ XA A 

sequentially at 
whatever speed 
you set them for. 
Easy to bund kK Includes pc board, 
parts and instructions. Ideal lor special 
lighting effects, costumes, etc. Oper- 
ates on 3 to 9 volts. PC board a 5" X 
2.25". A great one hour project. 
CAT* AEC $6.50 each 

STEPPING MOTOR 
CONTROLLER KIT 

Learn about 

stepping 

motors while 

building this 

simple circuit. 

includes circuit board, stepping motor 

and all parts except 12 Vdc power 

supply. CAT* SMKIT $18.00 each 

METRONOME KIT 




This simple device can be sal to click 
from 20 to 1 .000 beats per rrinute. 
Easy to build, includes circuit board, all 
components and inslructions. Oper- 
ates on a 9 volt battery (not included). 
CAT* METP.0 $3.75 each 



PHOTO RESISTOR 



a, 



Two piece holder. ** 3 
CAT*HLED 10 for 65c 



7r 



1 ,000 ohms bright light. 
16K ohms dark. 
0.182" dia, X .08-high, 0.18" long leads. 
CAT#PHE-7 2lor$1.00 
100 lor $45.00 ■ 1000 lor $400.00 



ORDER TOLL FREE 1-800-826-5432 



FAX (818) 781-2653 • INFORMATION (818) 904-0524 
Call Or Write For Our 




Free 60 Page Catalog 

Outside the U.S.A. send $2.00 
postage for a catalog. 



Minimum Order $10.00 * All Orders Can Be Charged To Visa, Mastercard 
Or Discovercard • Checks and Money Orders Accepted By Mail • California, Add 
Sales Tax • Shipping And Handling $3.50 For the 48 Continental United States - 
All Others Including Alaska, Hawaii, PR. And Canada Must Pay Full Shipping • 4»JV 



Quantities Limited • No COD. • Prices Subject to change without notice. 



5 



MAIL ORDERS TO: ALL ELECTRONICS CORP • P.O. BOX 567 • VAN NUYS, CA 91408 



CIRCLE 107 ON FREE INFORMATION CARD 



93 



Top Performance 



GoldStar 20MHz Oscilloscope 








Global Specialties Protoboard® Design Station 



Features: 

■ 6" rectangular CRT display, internal graticule & scale 

• Phase difference measurements between two signals using 
X-Y scope or Dual Trace 

- Two different scale probes: x1 and x1 

• Bandwidth from DC to 20MHz 

• Includes: Two 40MHz probes, two fuses, power cord, operation manual, 
schematics and block and wiring diagrams 

■ High sensitivity: 1 mWdiv 

■ Two-year manufacturer's warranty 

GS7020 $499.95 




Features: 

• Ideal for analog, digital and microprocessor 
circuits 

• Triple DC regulated power supplies, +5V. 
+15V, -15V 

-8 logic indicators 

• Function generator with sine, square, 
triangle and TTL waveforms 



■ Two debounced push-button switches 

■ Two SPOT slide switches, all leads 
available and uncommited 

■ A total of 2520 uncommited tie-points 

■ Potentiometers: one 1 K£2 and one 10K 

■ Includes power supply, instrumentation 
and bread boarding 



Jameco Logic Pulser 




■ Compatible wild TTL, DTI. RTL. HTL. 
HNIL, MOS and CMOS ICs. • IMfl Syne 
input impedance * Pulser mode output 
current: 10mA ■ Square wave current 
output: 5mA ■ Audible lone 

LP540 $16.95 



PROTOTYPING PRODUCTS 
Jameco Solderless Breadboards 



Jameco Logic Probe 




■ Max Frequency 80MHz * Minimum delectable 
pulse 10ns • 120K12 input impedance - Max. 
supply voltage: ;2SV • TTL threshold: (Lo]»0.8V 
:0.1V [Hi) -2.3V :0.2V ■ CMOS threshold: 
(Lo)3u% VCC :10Ti (Hi) 70%VCC =10% 



PB503. $299. 



A.R.T. EPROM Programmer 




■ Programs all current EPROMs in the 2716 to 
27512 range plus the X2864 EEPROM 
• RS232 port ■ Software included 



UVP EPROM Eraser 



r" 



■ Erases all EPROM's • Erases 1 chip ir 

15 minutes and S chips in 21 min 
• UV intensity: 6800 UVWCM 2 



MS104 $24.95 EPP $199,95 DE4. 



.$79. 



Metex Digital Multimeters 




General Specs: 
■ Handheld, high 
accuracy ■ ACVDC 
voltage. ACiDC 
current, resistance, 
diodes, continuity, 
transistor hFE 
• Manual ranging w,' 
overload protection 



H36S0 1 M46S0 only: 

• Also measure Frequency and capacitance 



M4650 only: - Data held switch * 4.5 digit 




Dim. 
L- X W" 



JE21 
JE23 
JE24 
JE25 
JE26 
JE27 



3.25 x 2.125 
6.5x2.125 
6,5x3.125 
6.5x4.25 
6.875 X 5.75 
7.25 1 7.5 



400 

S30 
1,360 
1.560 
2.390 
2.220 



$4.95 

S6.95 

Z S12.95 

3 S17.95 
i S22.9S 

4 S32.9S 



J AMECO 

24 Hour Order Hotline 

(415)592-8097 



FAX: (415) 592-2503 
(415) 595-2664 



M3610 
M3650 



114650 



3.5 uitjt MuHimelH $59.95 

3.5 Digrt MuHimeier ^Frequency & 
Capacitance $74.95 

45 rjigdw.'FrBouency, Capacitance 

and Data HcM Switch S99.95 



Handheld Multimeter 



• 3-5 digit LCD with automatic polarity indication 
■ ACJDC voltage measurement up to 500 volts 

- ACi'DC current measurement up to 200mA 

- Resistance measurement up lo 20tVi..' - Con, 
lirtulty checker with audible tone • Diode and 
logic tester ► Auto/manual range and data hold 
f unctions * All range protection and Function in, 
dications 



EPROMs - for your programming needs 



Part. No.. 



Price 



TMS2516 

TMS2532-35 

TMS2532A 

TMS2564 

TMS2716 

1702A 

2708 

2716 

2716-1 

27C16 

2732 

2732A-20 

2732A-25 

2732A-45 

27C32 



$4.25 
9.95 
7.95 
5.95 
5.95 
3.95 
4.95 
3.49 
3.95 
4.25 
4.95 
3.95 
3.49 
2.95 
3.95 



Part No- 



Price Part No. 



_Pn 



2764-20 

2764-25 

2764-45 

2764A-20 

2764A-25 

27C64-15 

27C64-25 

271280TP 

27128-20 

27128-25 

27128A-15 

27128A-20 

27128A-25 

27C1 28-15 

27C1 28-25 



$3.95 
3.75 
3.49 
3.95 
3.25 
3.95 
3.25 
2.95 
6.95 
4.95 
5.95 
4.49 
4.25 
5.95 
5.75 



272560TP 

27256-15 

27256-20 

27256-25 

27C256-15 

27C256-20 

27C256-25 

2751 20TP 

27512-20 

27512-25 

27C512-15 

27C512-20 

27C512-25 

27C010-15 

68766-35 



$3. 

5. 

5. 

4. 

5. 

4. 

4. 

4. 

6. 

5. 

6. 

6. 

5. 
11. 

9. 



Soldering and Desoldering Stations 

60 Watt Analog Display Soldering Station - Electronic 
temperature control (rem 200° to 878 F ■ Cartridge heat- 
ing element for a longer life of the soldering tip 

XY1683 $69.95 




30 Watt Electronic Temperature Controlled Desoldering 
Station - Electronic temperature control from 212° to 
842" F • Self contained high rotary vacuum pump 

DMM905 $39.95 XY999 $299.95 



94 



• Partial Listing • Over 4000 Electronic and Computer Components in Stock! 

CIRCLE 114 ON FREE INFORMATION CARD 



Widest Selection 



otm^JKJSm? 



t\etv\ s 



aod 



E\e< 



c\to^ vC 



Assemble Your own Computer Kit! 

Jameco 16MHz 80386SX Desktop Computer Kit 

jilding your own computer provides you with a better understanding of 

mponents and their (unctions 

-depth assembly instructions included 

we your new computer assembled and running in an evening, 

ing common tools 

jftware included 

irchase computer kits configured by Jameco or design your own 



imeco 16MHz 30386SX 
esktop Computer Kit 

udes: 

I386SX Motherboard with 

^B RAM (expandable to 8MB) 

)l-key enhanced keyboard 

ulti I/O Card 

ishiba 1.44MB, 3.5" DSHD 

ippy disk drive 

jby sized desktop case 

)0 Watt power supply 

R DOS S.O by Digital 

ssearch and Diagsoft's 

APIus diagnostic software 



^£3816 



.95 





Hard 
Drives 



Conner {16-bit IDE) 

CP3044 40UB 3.5' Low Profile $469.95 

CP3184 80MB 3.5'HH $649.95 

CP3104 !0DMB 35'HH $699.95 

ADP20 Host Adapter, $29.95 

Rellsys 14" VGA 
Color Monitor 




■ Max resolution : 720 x 480 

■ Bandwidth :30MHz 

■ Input: DB1 5-pin (analog) 

RE9513 $449.95 

Jameco 16-bit VGA Card 




• Supports VGA. EGA. EGA. MDA and 
Hercules modes ■ Conies with 256KB 
video RAM upgradable to 512KB (eight 
41464-80) ■ Capable of 640 x 480 with 
256 colors, 800 x 600 with 16 colors 

VG200O $149.95 



Integrated Circuits 



INo. 


1-9 


19t 


Part No. 


1-9 


lOt 


a 


$.29 


$.19 


7472 


$.39 


$.29 


2 


.29 


.19 


7473 


.39 


.29 


4 


,29 


.19 


7474 


.39 


.29 


5 


.35 


.25 


7475 


.49 


.39 


6 


.39 


.29 


7476 


.45 


.35 


7 


.39 


.29 


7483 


.69 


.59 


8 


.35 


.25 


7486 


.45 


.35 





.29 


.19 


7469 


2.95 


2.75 


1 


.35 


.25 


7490 


.49 


.39 


4 


.35 


.25 


7493 


.45 


.35 


7 


.35 


.25 


74116 


1.19 


1.09 


:0 


.29 


.19 


74121 


.39 


.29 


:7 


.29 


.19 


74123 


.49 


.39 


a 


.29 


.19 


74125 


.49 


.39 


2 


.39 


.29 


74151 


39 


.29 


18 


.39 


.29 


74160 


.59 


.49 


2 


.49 


.39 


74161 


.69 


.59 


15 


.75 


.65 


74192 


.79 


.69 


16 


.89 


.79 


74193 


.79 


.69 


17 


.89 


.79 


74194 


.79 


.69 




Dynamic 


;RAMs 







Miscellaneous Components 

Potentiometers 

Values available (insert ohms into space marked "XX"): 
500Q. 1 K. 5K, 1 0K. 20K, 50K. 1 OOK, 1 MEG 

43PXX 3 « Watt, 15 Turn $,99 

63PXX '/2 Watl, 1 Turn $.89 





Transistors And Diodes 




PN2222 


..$.12 


1N4735.... 


....$.25 


2N4401 ... 


..$.15 


PN2907 


.....12 


2N3904,,,, 


12 


1N4148... 


07 


1N4004 


10 


1 N751 


15 


2N3055... 


69 


2N2222A .. 


25 


C106B1 .. 


49 


1N270 


25 



JMJT123 
206-8 
MPC121 
MS102 



Switches 

SPDT, On-On (Toggle) $1.25 

SPST. 1 S-pin (DIP) $1.09 

SPDT, CnOltOn (Toggje) S1 . 1 9 

SPST, Momentary (Push-Bulton) $.39 



D-Sub Connectors and Hoods 
DB25P Male, 25-pin $.65 1 DB25H Hood $.39 

DB25S Female. 25-pin... $.75 1 

LEDs 

XC209R T). (Red) $.141 XC556R T1 3 rt, (Red) ...$.12 

XC5S6G T1 3 M. (Green) .. .1 6 1 XC556Y J\ 3 H. (Yellow) .. .1 6 



IC Sockets 



4-100 


100ns, WK * 1 


$1.95 


41256-100 100ns, 256X11 


4-120 


120ns. 64K/1 


1.89 


41256-120 120ns.256K<1 


4-150 


150ns. 64k i 1 


1.75 


41256-150 150ns, 2S6K * 1 


56-50 


60ns, 256K * 1 


3.25 


51 1O00P-80 80ns. 1MB 1 1 


56-80 


80ns, 256K 1 1 


2.75 


511000P-10 100ns, 1M8x1 



$2.29 
2.19 
1.99 
8.95 
8.49 



• Call for a complete listing of IC's 



low Profile 

BLP 

141J> 

16LP,.., 

24LP 

28LP 

40LP 



Wire Wrap (Gold) Level #2 

8WW $.49 

14WW 65 

16WW ...69 

24WW 1.05 

28WW... 1.29 

40WW 1.79 

Soldenail Standard & Header Plug Sockets Also Available 



.$.11 
...12 
...13 

... .19 
... .22 
... .28 



24 Hours A Day! 



J AMECO 

24 Hour Order Hotline 
(415)592-8097 

FAX: (415) 592-2503 
{415)595-2664 

1355 Shore way Road 
Belmont, CA 94002 

Look to Jameco 



• Wide selection of integrated 
circuits and components 

• Quality prototype and test 
equipment 

• Computer kits and accessories 
Additional items that Jameco offers; 

• Tools 

• Cables 

■ Connectors 

• Data Boohs 

• Motherboards 

• Memory 

■ Math Coprocessors 

• Computer Accessories 

■ Power Protection Equipment 

• Much, much more ! 

Let us show you what we have to offer; 
call or write for the latest Jameco catalog! 

$50.00 Minimum Order 

Data Sheets • 50e each 

For a FREE 90-Page catalog send $2,00 to cover 
first Class Postage and Handling 

© 1991 Jameco Electronics 5/91 

CA Residents Add 
6.00%, 6,50% or 7 00% Sales Tax 

Snipping, handling and insurance are additional- 
( Costs may vary according to wmghl and shipping method) 
Terms: Prices subject to change without notice. 
Items subject to availability and prior sale. 

Comptolo hst ot lefmsvw*ctant«s ht avajlawc upon r&quesl, 
IBM H a regitbflcad 1rad«iurk ol Insnf rjionnl Bunnasa UAChnH 



visa MMC 



Please 

refer to 

Mall Key 2 

when 
ordering 



Customer Service 'Technical Assistance • Credit Department • All Other Inquiries • {41 5) 592-8097 • 7AM - 4PM P.S.T. 

CIRCLE 114 ON FREE INFORMATION CARD 



£ 
5 



95 



c/j 
o 
z 
O 
£C 
\- 
O 

W 
-^ 
UJ 

Q 

< 

rr 
96 



SAVE MONEY. 
DON'T RENT! 



CABLE TV DESCRAMBLERS, 
CONVERTERS, & ACCESSORIES. 

Save hundreds of dollars 
owning instead of renting 
from the cable company 
Easy to order 
and install. 
Name brands- 
Pioneer, Oak, Panasonic, 
Jerrold, Scientific Atianta 
and more. 

We're famous for 
lowest prices, 
excellent service and immediate delivery. 
All products fully warranted. Your 
satisfaction is 100% guaranteed. 




CALL FOR FREE FULLY ILLUSTRATED 
16-PAGE COLOR CATALOG. 

(800)234-1006 



3 FORI 
SPECIAL 

ON SUB-MINIATURE VOICE 
FM TRANSMITTERS. 

KITS CONTAIN PC BOARDS 




-FMX-1 LONG RANGE (3 Ml) ULTRA SENSITIVE 
FM VOICE XMTR with fine tune, range control 
plus S34.50 

•TELX-1 TELEPHONE FM XMTR (3 Ml) auto- 
matically operates when phone is used. Crystal 
clear clarity with fine tune and range control. 
Non detectable ....S34.50 

m 

■ATR-1 AUTOMATIC TELEPHONE RECORDING 
DEVICE tapes telephone conversation all 
automatically $19.50 

ALL THREE OF ABOVE FOH :S69.50 

CALL OR SEND VISA, MASTER CHARGE, 
MONEY ORDER, ETC, TO AMAZING CONCEPTS. 
BOX 716, AMHERST, NH 03031. (603) 673-4730. 




ADVERTISING INDEX 



RADIO-ELECTRONICS does not assume any responsibility for errors that may appear in 
the index below. 



Free Information Number 



Page 



108 AMC Sales 16 

75 Ace Products 23 

107 All Electronics 93 

— Amazing Concepts 90,96 

84 Appliance Service 23 

67 Banner Technical Books 26 

98 Beckman Industrial 13 

109 C&S Sales CV3 

— CIE 3,31 

— Cable Ready Company 96 

180 Cable Warehouse 24 

— Command Productions 13 

58 Cook's Institute 16 

182 D&D Electronics 73 

187 Datak Corporation 24 

127 Deco Industries 23 

183 Electronic Goldmine 89 

— Electronics Book Club 5,81 

121 Fluke Manufacturing CV2 

176 General Technics .23 

192 Global Specialties 17 

— Grantham College 15 

86,193 Heathkit 27,64 

— Hi-Tech Electronics 23 

114 Jamcco ..94,95 

104 Jan Crystals 16 

1 15 Jensen Tools 23 

— King Wholesale 85 

87 MCM Electronics 87 

53 MI) Electronics 86 

93 Mark V. Electronics 91 

190 Matsushita Service Co 14 

61 Microprocessors Unltd 83 

117 Mouser 14 

— NRI Schools 21 

188 Optoelectronics 25 

56 Parts Express 89 

— Perfect Cable 88 

1 89 Peripheral Technology 83 

101 Pomona Electronics 7 

78 Radio Shack 32 



178 
181 



92 
123 

191 
179 
185 

186 



RE Reprint Bookstore 92 

SCO Electronics 71 

Sencore CV4 

Star Circuits 26 

Tech Spray, Inc 26 

Tektronix 1 1 

Test Probes 73 

The SPEC-COM Journal 13 

Unicorn 88 

U.S. Cable 71 

Vicjo Publications 27 

WPT Publications 76' 

Wholesale Cable 91 



ADVERTISING SALES OFFICE 

Gernsback Publications, Inc. 
500 B Bi County Blvd. 
Farmingdale, NY 11735 
1 (516) 293-3000 
President: Larry Steckler 

For Advertising ONLY 
516293 3000 
Fan 1-516-293-3115 
Larry Steckler 

publisher 
Christina Estrada 

assistant to the President 
Arline Fish man 

advertising director 
Denise Haven 

advertising assistant 
Kelly McQuade 

credit manager 

Subscriber Customer Service 

1-BO0-288-O652 

Order Entry for New Subscribers 

1-800-999-7139 

7:00 AM - 6:00 PM M-F MST 

SALES OFFICES 

EAST/SOUTHEAST 

Stanley Levitan, Eastern Sales Manager 

Radio-Electronics 

259-23 57th Avenue 

Little Neck, NY11362 

1-718-428-6037. 1-516-293-3000 

Fan 1-718-225-8594 

MIDWEST/Texas/Arkansas/Okla. 

Ralph Bergen, Midwest Sales Manager 

Radio- Electronics 

540 Frontage Road — Suite 339 

Northfield, IL 60093 

1-708-446-1444 

Fax 1-708-446-8451 

PACIFIC COAST/Mountain States 

Marvin Green, Pacific Sales Manager 

Radio- Electronics 

5430 Van Nuys Blvd. Suite 316 

Van Nuys. CA 91401 

1-818-986-2001 

Fax 18 18-986-2009 

RE Shopper 

Joe Shere, National Representative 

P.O. Box 169 

Idyll wild, CA 92349 

1-714-659-9734 

Fax 1-714-659-2469 



48ho UR ELENCO & HITACHI PRODUCTS 4S hour 
shipping AT DISCOUNT PRICES SHiPPING 



Hitachi RSO Series 

(Portabla Real-time Digital Storage Oscilloscopes) 

VC-S023 - 20MHz, 20MS/S S99/mo - 

50MHz, 20MS/S $120/mo" 

50MHz. 20MS/S $135/mo' 

SIESfrno' 

$200/mo" 



VC-6024 
VC-6025 
VG-604S 
VC-6145 



LEASING AVAILABLE 

For all Hitachi Scopat - Call for details 
' Based on 24 months except V-l 150, VC-6045, VC- 
6145 (36 monliis) 



100MHz. 40MSte_ 



100MHz, 100MS/s_ 



RSO's from Hilaehi feature roll mode, averaging, save 
memory, smoothing, interpolation, pretrigg Bring, cursor 
measurements. These scopes enable more accurate, 
simplisr observation of complex waveforms, in addition to 
such functions as haidcopy via a plotter interface and 
waveform transfer via lha RS-232C interlace. Enjoy the 
comlott of analog and I he power (o digital. 

20MHz Elenco Oscilloscope 

$375 

M0-12S1 

■ Dual Trace 

Component Tester 

• 6' CRT 

• X-Y Operation 

• TV Sync 

• 2 P-1 Probes 



Hitachi Portable Scopes 
DC to 50MHz. 2-Channel, DC offcet (unc- 
tion, Alternate magnifier; function 
V-525 • CRT Readout. Cursor Meas. _ $1,025 

V-523 - Delayed Sweep $995 

V-522 - Basic Model _ $895 

V-422-40MHz $795 

V-223 - 20Mhz delayed sweep $695 

V-212 - 20MHz $425 



HITACHI COMPACT SERIES SCOPES 

This series provides many new lunctions such as CRT 
Readout, Cursor measurements (V- 1085/1 065/665), Fre- 
quency Ctr (V-1085), Swflflptimo Auto ranging. Delayed 
sweep and Tripper Loch using a 6-inch CRT. You dont feel 
the compactness in terms of performance and operation. 



V-660 
V-665 



60MHz, Dual Trace_ 



60MHz, DT. wrcursor 

V-1060 - 100MHz, Dual Traca 

V-1065 - 100MHz. DT, w/cursor 
V-1085 - 100MHz, QT, w/cursor_ 
V-1 1 00 A - 1 00MHz, Quad Trace^ 
V-1150 - 150MHz, Quad Trace 



_$1.195 
$1,345 
$1,425 
$106Vmo' 
SUSVmo' 
_$125/mo' 
_$115/mo' 



Elenco 35MHz Dual Trace 

50MHz *H33 
MO- 1252 

• High luminance 6' CRT 

• 1mV Sensitivity 
• 6KV Acceleration Voltage 

• 1 0ns Rise Time 

• X-Y Operation • 1 Axis 
• Delayed Triggering Sweep 

• Includes 2 P-1 Probes 

All scopes include probes, schematics, operators manual and 3 year (2 yrs for Elenco scopes) world wide warranty on parts a labor. Many accessories available for all Hitachi 
scopes. Call or write for complete specif cations on these and many other fine oscilloscopes. 




FREE DMM 

with purchase of 

ANY SCOPE 



SCOPE PROBES 

P-1 65MHz. lx, lOx $19.95 

P-2 100MHz, lx, lOx $23.95 




B + K 

TEST EQUIPMENT 
All Models Available 

Call for special price 



Digital Capacitance Meter 
CM-1550B 

$58.95 

9 Ranges 

.1pf-20.OOuuld 

.5% basic accy. 

Zero control w/ Case 

Big 1' Display 




Digital LCR Meter 
LC-1801 
$125 

Measures; 

Coils 1UH-200H 

Cap5,1pf-200ul 

»55e Res .01 -20 W 



Multimeter with 
Capacitance ft 
Transistor Tester 

$55 CM-1500B 
Reads Volts, Ohms 
Current, Capacitors. 
|,iiil^ Transistors and 

Diodes t with case 
Big 1" Display 




FLUKE 

MULTIMETERS 
All Models 
Available 

Call for special piice 



Quad Power Supply 



XP-580 

$59.95 

2 -20V @ 2A 

12V @1A 

5V@3A 

■5V § .5A 

Fully regulated and short circuit protected 




Triple Power Supply XP-620 
Assembled $65 
Kit $45 

2to15V@1A, 

-2to-15V@1A 

(or 4 to 30V @1 A) 

and F V @ 3A 

Ail the desired lealures for doing experiments. 
Features short circuit protection, all supplies 




AM/FM Transistor 

Radio Kit 
with Training Course 

Model AM' FM 108 

$26.95 

14 Transistors 4 5 Diodes 
Makes a great school project 




True RMS 4 1/2 
Digit Multimeter 
M-7000 

$135 

.0514 DC Accuracy 

.1% Resistance 

with Fraq. Courtier 

and Deluia Case 



GF-8016 Function Generator 

with Freq. Counter 




$249 



Sine. Square. Triangle 
Pulse, Ramp, .2 lo 2MHz 
Freq Counter .1 - 10MHz 



GF-801S without Freq. Meter $179 



Function Generator 
5 --,:■ ' i Blox 

"...r~r! $28.95 

Provides sine, triangle, square 

wave Item 1Hz to 1MHz 

AM or I M capabiEity 



Learn to Build and Program 
Computers with this Kit 

Includes: All Parts, Assembly and Lesson Manual 

Model 
mm-booq 



Wide Band Signal 
Generators 




$129.00 




Starting from scratch you build a certiorate system . Our 
V4CTQ Mas ti?r trainer teachas you lo write into RA Ms. 
ROMs and run a -80S5 micrcpfoceKor, which uses 
similar machine language as IBM PC. 

Robotics Kit for above (MM8010) 71.95 



WE WILL NOT BE UNDERSOLD! 
UPS Shipping: 46 States 5% 
{$3 Mm $10 Max) Shipping 
IL Res., 7% Tax FAX: 708-520-0085 



SG-9000 $129 

RF Req 1MK-450Mrte AM Modula- 
tion of IKHz Variable RF output 
SG-9500 m/ Digital Display t 
150MH; built-in Counter S249 



XK-500 DIGITAL / ANALOG TRAINER 

A complete mlnUlab for building, toiling, prototyping analog and digital circuits 

EI*nWt Digital ■' Analog TralfUji ;t Spet&'iy ooiignM 1or jCIhhiI propels. -*:ih S BM In pOwflr supplies. 
Includti a twicSoh nortdrator imjh contlnouilif vaHiWB L tin*, irlsnguuu, iquara *»« tornu. A* powar 
■uppikn ara rogu jt»a afldpr0t«(W against Shorn 

POWER SUPPLIES 

■ Vs'otM* Pewiv Svoptf 

• *1.2Sto90VDCtV -5 Amp 

{+l.MluiSVDCC 1 A«|3] 

♦ -l,Sto-MVPC(f iAmp 

» .iSVDC^iAmp 

* -12VDCC 1 Amp 

• ♦SVDCflHiMnp 

■ 3QVAC Canhw ripc*3 tj ISVAC 
dlAmp 

ANALOG -SECTION 
- Firetcn GvvtKt Sin*, TriinguUr. 
ITlJMrtWHIIIllTIH 

* Froqijifleir*^*"^ « '« rtngtt 
Uom 1 10 1Q0KH7 



DIGITAL - SECTION 

» Twq no bpunc* *>yt MHtH 

- E-ght LEOrudoLtis TTL &jflr»wJ 

- Cbcfc \iKU9tHrt 1 la lM^III 

■ Ckso. atT¥rlj1uct4 SVPP kjuJ.-c wi-n 

BREADBOARDS 

* 2 FJnadtxunti. hcTi ccniti 
twO 14 porti (total 1 ,WD r 




C & S SALES INC. 

1245 Rosewood. Deerfield, IL 60015 

l«IMH2«-7711 f 70S I 541-0710 



15 Day Money Back Guarantee 

2 Year Warranty fv .cm subject to change 

WRITE FOR FREE CATALOG 



CIRCLE 109 ON FREE INFORMATION CARD 



Introducing a new companion to your 
VA62A Universal Video Analyzing System! 



Isolate All Playback Or Record Problems In All VCRs . . . 
Now And In The Future, Or Your Money Back! 




VA62A Universal Video Analyzer 



VC93 All Format VCR Analyzer 
'— - Patent Pending 

Now you'll have everything to completely analyze all VCR 
video, audio, and servo problems. 



Automatic Servo Analyzing: (patent pending) 
Automatically determine if the VCR has a capstan servo, cylinder 
servo, luminance/chrominance circuit defect in virtually the time 
it takes to connect to the video and audio line outputs.* 

Exclusive Video Head Substitution: 

Never again install another video head without being 100% positive 
it will fix the problem. Exclusive video head substitution signals 
isolate head problems from all other circuit problems. 

Exclusive Hi-Fi Stereo And Audio Signals: 

Finally there is an answer for troubleshooting VCR Hi-Fi audio 
circuits. Isolate defects from the spinning heads to the line outputs. 



Isolate Defects Throughout The Entire VCR: 

Exclusive phase- and chroma-locked drive signals isolate problems 
in any stage from the heads to the output. Every signal you need is 
there, including: FM luminance, chroma, video, and head switching 
(SW30) signals. 

Includes Extra Features To Complete Your Servicing Needs: 

You get: an Internal NTSC video pattern, standard video and audio 
line output, a servo sub bias supply to 10 VDC, an autoranged DC 
and PPV meter, plus it supports all common VCR formats, 

* Using the optional Servo Performance Test Leads and Servo 
Performance Test Tape. 



Call 1-800-SENGORE ext. 544 for more information! 



(736.2673) 

CIRCLE 181 OK FREE INFORMATION CARD